Making Invalid States Invalid in LiveView

Have you ever found a bug in your LiveView code because your app somehow had invalid and incoherent state?

“Your total is -$500.”
“Your return flight is .”
“The temperature is -600°F.”

When programming user interfaces, it’s important that we do not display inconsistent states to our users. But how can we prevent those bugs?

By making those invalid states impossible to represent!

Join me as we walk through a LiveView example that has bugs because of invalid states. As we fix them, you’ll learn to model domains in a way that makes rendering invalid states impossible. Your users and your future self will thank you.

Transcript

1. MAKING INVALID STATES INVALID in LiveView
2. MAKING INVALID STATES INVALID in LiveView AN EXPLORATION
3. WHAT DOES THAT MEAN?
4. How we model our domain constrains what states are allowed
5. Model our domain to remove states we don't want
6. NOT NEW
7. NOT NEW ▸ OCaml
8. NOT NEW ▸ OCaml ▸ Elm
9. NOT NEW ▸ OCaml ▸ Elm ▸ F#
10. OTHER NAMES
11. OTHER NAMES ▸ Making invalid states unrepresentable
12. OTHER NAMES ▸ Making invalid states unrepresentable ▸ Making illegal states unrepresentable
13. OTHER NAMES ▸ Making invalid states unrepresentable ▸ Making illegal states unrepresentable ▸ Making impossible states impossible
14. BRINGING IT TO LiveView
15. BRINGING IT TO LiveView ▸ Persistent state
16. BRINGING IT TO LiveView ▸ Persistent state ▸ That our users see
17. A FLIGHT BOOKER EXAMPLE !
19. FIRST IMPLEMENTATION
20. ASSIGNING VALUES def mount(_, _, socket) do { :ok, socket |> assign(:direction, "one-way") |> assign(:departure, Date.utc_today()) |> assign(:return, nil) } end
21. ASSIGNING VALUES def mount(_, _, socket) do { :ok, socket |> assign(:direction, "one-way") |> assign(:departure, Date.utc_today()) |> assign(:return, nil) } end
22. RENDERING THE ASSIGNS <form phx-submit="book"> <%= select :booking, :flight_type, ["one-way", "two-way"], value: @direction %> <%= text_input :booking, :departure, value: @departure %> <%= text_input :booking, :return, value: @return %> <%= submit "Book" %> </form>
23. RENDERING THE ASSIGNS <form phx-submit="book"> <%= select :booking, :flight_type, ["one-way", "two-way"], value: @direction %> <%= text_input :booking, :departure, value: @departure %> <%= text_input :booking, :return, value: @return %> <%= submit "Book" %> </form>
24. RENDERING THE ASSIGNS <form phx-submit="book"> <%= select :booking, :flight_type, ["one-way", "two-way"], value: @direction %> <%= text_input :booking, :departure, value: @departure %> <%= text_input :booking, :return, value: @return %> <%= submit "Book" %> </form>
25. RENDERING THE ASSIGNS <form phx-submit="book"> <%= select :booking, :flight_type, ["one-way", "two-way"], value: @direction %> <%= text_input :booking, :departure, value: @departure %> <%= text_input :booking, :return, value: @return %> <%= submit "Book" %> </form>
26. HANDLING THE EVENT def handle_event("book", %{"booking" => params}, socket) do {:ok, message} = FlightBooker.book_trip(params) socket |> put_flash(:info, message) |> noreply() end
27. HANDLING THE EVENT def handle_event("book", %{"booking" => params}, socket) do {:ok, message} = FlightBooker.book_trip(params) socket |> put_flash(:info, message) |> noreply() end
28. BOOKING THE TRIP def book_trip(params) do case params do %{"flight_type" => "one-way", "departure" => departure} -> {:ok, one_way_message(departure)} %{"flight_type" => "two-way", "departure" => departure, "return" => return} -> {:ok, two_way_message(departure, return)} end end
29. BOOKING THE TRIP def book_trip(params) do case params do %{"flight_type" => "one-way", "departure" => departure} -> {:ok, one_way_message(departure)} %{"flight_type" => "two-way", "departure" => departure, "return" => return} -> {:ok, two_way_message(departure, return)} end end
30. BOOKING THE TRIP def book_trip(params) do case params do %{"flight_type" => "one-way", "departure" => departure} -> {:ok, one_way_message(departure)} %{"flight_type" => "two-way", "departure" => departure, "return" => return} -> {:ok, two_way_message(departure, return)} end end
32. ! THE BUGS
33. ! THE BUGS
34. ! THE BUGS ▸ ! One-way flight that got charged for a return flight
35. ! THE BUGS ▸ ! One-way flight that got charged for a return flight ▸ " Two-way flight without a return flight
36. OUR CURRENT (IMPLICIT) DOMAIN MODEL %{ direction: "one-way" | "two-way", departure: Date.t() | nil, return: Date.t() | nil }
37. OUR CURRENT (IMPLICIT) DOMAIN MODEL %{ direction: "one-way" | "two-way", departure: Date.t() | nil, return: Date.t() | nil }
38. OUR CURRENT (IMPLICIT) DOMAIN MODEL %{ direction: "one-way" | "two-way", departure: Date.t() | nil, return: Date.t() | nil }
39. OUR CURRENT (IMPLICIT) DOMAIN MODEL %{ direction: "one-way" | "two-way", departure: Date.t() | nil, return: Date.t() | nil }
40. OUR CURRENT (IMPLICIT) DOMAIN MODEL %{ direction: "one-way" | "two-way", departure: Date.t() | nil, return: Date.t() | nil }
41. POSSIBLE STATES # one-way %{direction: "one-way", departure: Date.t(), return: Date.t()} %{direction: "one-way", departure: nil, return: Date.t()} %{direction: "one-way", departure: Date.t(), return: nil} %{direction: "one-way", departure: nil, return: nil} # two-way %{direction: "two-way", departure: Date.t(), return: Date.t()} %{direction: "two-way", departure: nil, return: Date.t()} %{direction: "two-way", departure: Date.t(), return: nil} %{direction: "two-way", departure: nil, return: nil}
42. POSSIBLE STATES # one-way %{direction: "one-way", departure: Date.t(), return: Date.t()} %{direction: "one-way", departure: nil, return: Date.t()} %{direction: "one-way", departure: Date.t(), return: nil} %{direction: "one-way", departure: nil, return: nil} # two-way %{direction: "two-way", departure: Date.t(), return: Date.t()} %{direction: "two-way", departure: nil, return: Date.t()} %{direction: "two-way", departure: Date.t(), return: nil} %{direction: "two-way", departure: nil, return: nil}
43. POSSIBLE STATES # one-way %{direction: "one-way", departure: Date.t(), return: Date.t()} %{direction: "one-way", departure: nil, return: Date.t()} %{direction: "one-way", departure: Date.t(), return: nil} %{direction: "one-way", departure: nil, return: nil} # two-way %{direction: "two-way", departure: Date.t(), return: Date.t()} %{direction: "two-way", departure: nil, return: Date.t()} %{direction: "two-way", departure: Date.t(), return: nil} %{direction: "two-way", departure: nil, return: nil}
44. INVALID STATES # one-way %{direction: "one-way", departure: Date.t(), return: Date.t()} %{direction: "one-way", departure: nil, return: Date.t()} %{direction: "one-way", departure: Date.t(), return: nil} %{direction: "one-way", departure: nil, return: nil} # two-way %{direction: "two-way", departure: Date.t(), return: Date.t()} %{direction: "two-way", departure: nil, return: Date.t()} %{direction: "two-way", departure: Date.t(), return: nil} %{direction: "two-way", departure: nil, return: nil}
45. VALID STATES # one-way %{direction: "one-way", departure: Date.t(), return: Date.t()} %{direction: "one-way", departure: nil, return: Date.t()} %{direction: "one-way", departure: Date.t(), return: nil} %{direction: "one-way", departure: nil, return: nil} # two-way %{direction: "two-way", departure: Date.t(), return: Date.t()} %{direction: "two-way", departure: nil, return: Date.t()} %{direction: "two-way", departure: Date.t(), return: nil} %{direction: "two-way", departure: nil, return: nil}
46. ONLY 2/8 STATES ARE VALID! # one-way %{direction: "one-way", departure: Date.t(), return: nil} # two-way %{direction: "two-way", departure: Date.t(), return: Date.t()}
47. A MORE constrained FLIGHT BOOKER DOMAIN MODEL
48. A MORE constrained FLIGHT BOOKER DOMAIN MODEL
49. A MORE constrained FLIGHT BOOKER DOMAIN MODEL ▸ One-way flight with departure date
50. A MORE constrained FLIGHT BOOKER DOMAIN MODEL ▸ One-way flight with departure date ▸ OR
51. A MORE constrained FLIGHT BOOKER DOMAIN MODEL ▸ One-way flight with departure date ▸ OR ▸ Two-way flight with departure and return dates
52. A MORE constrained FLIGHT BOOKER DOMAIN MODEL @type flight_booker :: {:one_way, Date.t()} | {:two_way, Date.t(), Date.t()}
53. A MORE constrained FLIGHT BOOKER DOMAIN MODEL @type flight_booker :: {:one_way, Date.t()} | {:two_way, Date.t(), Date.t()}
54. A MORE constrained FLIGHT BOOKER DOMAIN MODEL @type flight_booker :: {:one_way, Date.t()} | {:two_way, Date.t(), Date.t()}
55. TAGGED VALUES defmodule FlightBooker do def one_way(%Date{} = date) do {:one_way, date} end def two_way(%Date{} = departure, %Date{} = return) do {:two_way, departure, return} end end
56. TAGGED VALUES defmodule FlightBooker do def one_way(%Date{} = date) do {:one_way, date} end def two_way(%Date{} = departure, %Date{} = return) do {:two_way, departure, return} end end
57. TAGGED VALUES defmodule FlightBooker do def one_way(%Date{} = date) do {:one_way, date} end def two_way(%Date{} = departure, %Date{} = return) do {:two_way, departure, return} end end
58. TAGGED VALUES defmodule FlightBooker do def one_way(%Date{} = date) do %OneWay{departure: date} end def two_way(%Date{} = departure, %Date{} = return) do %TwoWay{departure: departure, return: return} end end
59. TAGGED VALUES defmodule FlightBooker do def one_way(%Date{} = date) do %OneWay{departure: date} end def two_way(%Date{} = departure, %Date{} = return) do %TwoWay{departure: departure, return: return} end end
60. TAGGED VALUES defmodule FlightBooker do def one_way(%Date{} = date) do {:one_way, date} end def two_way(%Date{} = departure, %Date{} = return) do {:two_way, departure, return} end end
61. IMPLICATIONS OF OUR NEW DOMAIN MODEL
62. IMPLICATIONS OF OUR NEW DOMAIN MODEL ▸ Render complex types
63. IMPLICATIONS OF OUR NEW DOMAIN MODEL ▸ Render complex types ▸ Handle events with user input
64. 1. RENDER COMPLEX TYPE def mount(_, _, socket) do today = Date.utc_today() booker = FlightBooker.one_way(today) {:ok, assign(socket, :booker, booker)} end
65. 1. RENDER COMPLEX TYPE def mount(_, _, socket) do today = Date.utc_today() booker = FlightBooker.one_way(today) {:ok, assign(socket, :booker, booker)} end
66. 1. RENDER COMPLEX TYPE <form phx-submit="book" phx-change="update"> <%= case @booker do %> <% {:one_way, departure} -> %> <%= select :booking, :flight_type, ["one-way", "two-way"], value: "one-way" %> <%= text_input :booking, :departure, value: departure %> <%= text_input :booking, :return, disabled: true %> <% {:two_way, departure, return} -> %> <%= select :booking, :flight_type, ["one-way", "two-way"], value: "two-way" %> <%= text_input :booking, :departure, value: departure %> <%= text_input :booking, :return, value: return %> <% end %> <%= submit "Book" %> </form>
67. 1. RENDER COMPLEX TYPE <form phx-submit="book" phx-change="update"> <%= case @booker do %> <% {:one_way, departure} -> %> <%= select :booking, :flight_type, ["one-way", "two-way"], value: "one-way" %> <%= text_input :booking, :departure, value: departure %> <%= text_input :booking, :return, disabled: true %> <% {:two_way, departure, return} -> %> <%= select :booking, :flight_type, ["one-way", "two-way"], value: "two-way" %> <%= text_input :booking, :departure, value: departure %> <%= text_input :booking, :return, value: return %> <% end %> <%= submit "Book" %> </form>
68. 1. RENDER COMPLEX TYPE <form phx-submit="book" phx-change="update"> <%= case @booker do %> <% {:one_way, departure} -> %> <%= select :booking, :flight_type, ["one-way", "two-way"], value: "one-way" %> <%= text_input :booking, :departure, value: departure %> <%= text_input :booking, :return, disabled: true %> <% {:two_way, departure, return} -> %> <%= select :booking, :flight_type, ["one-way", "two-way"], value: "two-way" %> <%= text_input :booking, :departure, value: departure %> <%= text_input :booking, :return, value: return %> <% end %> <%= submit "Book" %> </form>
69. 1. RENDER COMPLEX TYPE <form phx-submit="book" phx-change="update"> <%= case @booker do %> <% {:one_way, departure} -> %> <%= select :booking, :flight_type, ["one-way", "two-way"], value: "one-way" %> <%= text_input :booking, :departure, value: departure %> <%= text_input :booking, :return, disabled: true %> <% {:two_way, departure, return} -> %> <%= select :booking, :flight_type, ["one-way", "two-way"], value: "two-way" %> <%= text_input :booking, :departure, value: departure %> <%= text_input :booking, :return, value: return %> <% end %> <%= submit "Book" %> </form>
70. 1. RENDER COMPLEX TYPE <form phx-submit="book" phx-change="update"> <%= case @booker do %> <% {:one_way, departure} -> %> <%= select :booking, :flight_type, ["one-way", "two-way"], value: "one-way" %> <%= text_input :booking, :departure, value: departure %> <%= text_input :booking, :return, disabled: true %> <% {:two_way, departure, return} -> %> <%= select :booking, :flight_type, ["one-way", "two-way"], value: "two-way" %> <%= text_input :booking, :departure, value: departure %> <%= text_input :booking, :return, value: return %> <% end %> <%= submit "Book" %> </form>
71. FORCED TO HANDLE RETURN ON "ONE-WAY" FLIGHT <form phx-submit="book" phx-change="update"> <%= case @booker do %> <% {:one_way, departure} -> %> <%= select :booking, :flight_type, ["one-way", "two-way"], value: "one-way" %> <%= text_input :booking, :departure, value: departure %> <%= text_input :booking, :return, disabled: true %> <% {:two_way, departure, return} -> %> <%= select :booking, :flight_type, ["one-way", "two-way"], value: "two-way" %> <%= text_input :booking, :departure, value: departure %> <%= text_input :booking, :return, value: return %> <% end %> <%= submit "Book" %> </form>
72. FORCED TO HANDLE RETURN ON "ONE-WAY" FLIGHT <form phx-submit="book" phx-change="update"> <%= case @booker do %> <% {:one_way, departure} -> %> <%= select :booking, :flight_type, ["one-way", "two-way"], value: "one-way" %> <%= text_input :booking, :departure, value: departure %> <%= text_input :booking, :return, disabled: true %> <% {:two_way, departure, return} -> %> <%= select :booking, :flight_type, ["one-way", "two-way"], value: "two-way" %> <%= text_input :booking, :departure, value: departure %> <%= text_input :booking, :return, value: return %> <% end %> <%= submit "Book" %> </form>
73. FORCED TO HANDLE RETURN ON "ONE-WAY" FLIGHT <form phx-submit="book" phx-change="update"> <%= case @booker do %> <% {:one_way, departure} -> %> <%= select :booking, :flight_type, ["one-way", "two-way"], value: "one-way" %> <%= text_input :booking, :departure, value: departure %> <% {:two_way, departure, return} -> %> <%= select :booking, :flight_type, ["one-way", "two-way"], value: "two-way" %> <%= text_input :booking, :departure, value: departure %> <%= text_input :booking, :return, value: return %> <% end %> <%= submit "Book" %> </form>
74. INVALID STATE REMOVED %{ direction: "one-way", departure: Date.t(), return: Date.t() }
75. 2. HANDLE EVENTS
76. TRANSFORM USER INPUT THROUGH PARSING
77. TRANSFORM USER INPUT THROUGH PARSING ▸ less structured data |> more structured data
78. TRANSFORM USER INPUT THROUGH PARSING ▸ less structured data |> more structured data ▸ raw data |> valid domain
79. TRANSFORM USER INPUT THROUGH PARSING ▸ less structured data |> more structured data ▸ raw data |> valid domain ▸ ⚠ |>
80. HANDLE EVENT def handle_event("book", %{"booking" => params}, socket) do {:ok, message} = params |> parse_params_into_booking() |> FlightBooker.book_trip() socket |> put_flash(:info, message) |> noreply() end
81. HANDLE EVENT def handle_event("book", %{"booking" => params}, socket) do {:ok, message} = params |> parse_params_into_booking() |> FlightBooker.book_trip() socket |> put_flash(:info, message) |> noreply() end
82. HANDLE EVENT def handle_event("book", %{"booking" => params}, socket) do {:ok, message} = params |> parse_params_into_booking() |> FlightBooker.book_trip() socket |> put_flash(:info, message) |> noreply() end
83. defp parse_params_into_booking(params) do case params do %{"flight_type" => "one-way", "departure" => departure} -> departure |> Date.from_iso8601!() |> FlightBooker.one_way() %{"flight_type" => "two-way", "departure" => departure, "return" => return} -> departure_date = departure |> Date.from_iso8601!() return_date = return |> Date.from_iso8601!() FlightBooker.two_way(departure_date, return_date) %{"flight_type" => "two-way", "departure" => departure} -> departure_date = departure |> Date.from_iso8601!() return_date = Date.utc_today() FlightBooker.two_way(departure_date, return_date) end end
84. defp parse_params_into_booking(params) do case params do %{"flight_type" => "one-way", "departure" => departure} -> departure |> Date.from_iso8601!() |> FlightBooker.one_way() %{"flight_type" => "two-way", "departure" => departure, "return" => return} -> departure_date = departure |> Date.from_iso8601!() return_date = return |> Date.from_iso8601!() FlightBooker.two_way(departure_date, return_date) %{"flight_type" => "two-way", "departure" => departure} -> departure_date = departure |> Date.from_iso8601!() return_date = Date.utc_today() FlightBooker.two_way(departure_date, return_date) end end
85. defp parse_params_into_booking(params) do case params do %{"flight_type" => "one-way", "departure" => departure} -> departure |> Date.from_iso8601!() |> FlightBooker.one_way() %{"flight_type" => "two-way", "departure" => departure, "return" => return} -> departure_date = departure |> Date.from_iso8601!() return_date = return |> Date.from_iso8601!() FlightBooker.two_way(departure_date, return_date) %{"flight_type" => "two-way", "departure" => departure} -> departure_date = departure |> Date.from_iso8601!() return_date = Date.utc_today() FlightBooker.two_way(departure_date, return_date) end end
86. defp parse_params_into_booking(params) do case params do %{"flight_type" => "one-way", "departure" => departure} -> departure |> Date.from_iso8601!() |> FlightBooker.one_way() %{"flight_type" => "two-way", "departure" => departure, "return" => return} -> departure_date = departure |> Date.from_iso8601!() return_date = return |> Date.from_iso8601!() FlightBooker.two_way(departure_date, return_date) %{"flight_type" => "two-way", "departure" => departure} -> departure_date = departure |> Date.from_iso8601!() return_date = Date.utc_today() FlightBooker.two_way(departure_date, return_date) end end
87. defp parse_params_into_booking(params) do case params do %{"flight_type" => "one-way", "departure" => departure} -> departure |> Date.from_iso8601!() |> FlightBooker.one_way() %{"flight_type" => "two-way", "departure" => departure, "return" => return} -> departure_date = departure |> Date.from_iso8601!() return_date = return |> Date.from_iso8601!() FlightBooker.two_way(departure_date, return_date) %{"flight_type" => "two-way", "departure" => departure} -> departure_date = departure |> Date.from_iso8601!() return_date = Date.utc_today() FlightBooker.two_way(departure_date, return_date) end end
88. defp parse_params_into_booking(params) do case params do %{"flight_type" => "one-way", "departure" => departure} -> departure |> Date.from_iso8601!() |> FlightBooker.one_way() %{"flight_type" => "two-way", "departure" => departure, "return" => return} -> departure_date = departure |> Date.from_iso8601!() return_date = return |> Date.from_iso8601!() FlightBooker.two_way(departure_date, return_date) %{"flight_type" => "two-way", "departure" => departure} -> departure_date = departure |> Date.from_iso8601!() return_date = Date.utc_today() FlightBooker.two_way(departure_date, return_date) end end
89. defp parse_params_into_booking(params) do case params do %{"flight_type" => "one-way", "departure" => departure} -> departure |> Date.from_iso8601!() |> FlightBooker.one_way() %{"flight_type" => "two-way", "departure" => departure, "return" => return} -> departure_date = departure |> Date.from_iso8601!() return_date = return |> Date.from_iso8601!() FlightBooker.two_way(departure_date, return_date) %{"flight_type" => "two-way", "departure" => departure} -> departure_date = departure |> Date.from_iso8601!() return_date = Date.utc_today() FlightBooker.two_way(departure_date, return_date) end end
90. INVALID STATE REMOVED %{ direction: "two-way", departure: Date.t(), return: nil }
91. defp parse_params_into_booking(params) do case params do %{"flight_type" => "one-way", "departure" => departure} -> departure |> Date.from_iso8601!() |> FlightBooker.one_way() %{"flight_type" => "two-way", "departure" => departure, "return" => return} -> departure_date = departure |> Date.from_iso8601!() return_date = return |> Date.from_iso8601!() FlightBooker.two_way(departure_date, return_date) %{"flight_type" => "two-way", "departure" => departure} -> departure_date = departure |> Date.from_iso8601!() return_date = Date.utc_today() FlightBooker.two_way(departure_date, return_date) end end
92. INVALID STATES REMOVED %{direction: "one-way", departure: nil, return: nil} %{direction: "one-way", departure: nil, return: Date.t()} %{direction: "two-way", departure: nil, return: nil} %{direction: "two-way", departure: nil, return: Date.t()}
93. Without any error handling, we have removed 6 invalid states!
94. WHAT ABOUT ERROR HANDLING?
95. WHAT ABOUT ERROR HANDLING? ▸ Validate and present errors
96. WHAT ABOUT ERROR HANDLING? ▸ Validate and present errors ▸ Potential for same problems
97. POSSIBLE ERRORS @type error_fields :: :departure | :return @type errors :: [error_fields]
98. ADDING ERRORS ASSIGN socket |> assign(:direction, "one-way") |> assign(:departure, Date.utc_today()) |> assign(:return, nil) + |> assign(:errors, [])
99. (PREVIOUS) POSSIBLE STATES # one-way %{direction: "one-way", departure: Date.t(), return: Date.t()} %{direction: "one-way", departure: nil, return: Date.t()} %{direction: "one-way", departure: Date.t(), return: nil} %{direction: "one-way", departure: nil, return: nil} # two-way %{direction: "two-way", departure: Date.t(), return: Date.t()} %{direction: "two-way", departure: nil, return: Date.t()} %{direction: "two-way", departure: Date.t(), return: nil} %{direction: "two-way", departure: nil, return: nil}
100. (PREVIOUS) POSSIBLE STATES # one-way %{direction: "one-way", departure: Date.t(), return: Date.t()} %{direction: "one-way", departure: nil, return: Date.t()} %{direction: "one-way", departure: Date.t(), return: nil} %{direction: "one-way", departure: nil, return: nil} # two-way %{direction: "two-way", departure: Date.t(), return: Date.t()} %{direction: "two-way", departure: nil, return: Date.t()} %{direction: "two-way", departure: Date.t(), return: nil} %{direction: "two-way", departure: nil, return: nil}
101. # one-way %{direction: "one-way", departure: Date.t(), return: Date.t(), errors: []} %{direction: "one-way", departure: Date.t(), return: Date.t(), errors: [:departure]} %{direction: "one-way", departure: Date.t(), return: Date.t(), errors: [:return]} %{direction: "one-way", departure: Date.t(), return: Date.t(), errors: [:departure, :return]} %{direction: "one-way", departure: nil, return: Date.t()} %{direction: "one-way", departure: Date.t(), return: nil} %{direction: "one-way", departure: nil, return: nil} # two-way %{direction: "two-way", departure: Date.t(), return: Date.t()} %{direction: "two-way", departure: nil, return: Date.t()} %{direction: "two-way", departure: Date.t(), return: nil} %{direction: "two-way", departure: nil, return: nil}
102. 8 X 4 = 32 POSSIBLE STATES! # one-way %{direction: "one-way", departure: Date.t(), return: Date.t(), errors: []} %{direction: "one-way", departure: Date.t(), return: Date.t(), errors: [:departure]} %{direction: "one-way", departure: Date.t(), return: Date.t(), errors: [:return]} %{direction: "one-way", departure: Date.t(), return: Date.t(), errors: [:departure, :return]} %{direction: "one-way", departure: nil, return: Date.t(), errors: []} %{direction: "one-way", departure: nil, return: Date.t(), errors: [:departure]} %{direction: "one-way", departure: nil, return: Date.t(), errors: [:return]} %{direction: "one-way", departure: nil, return: Date.t(), errors: [:departure, :return]} %{direction: "one-way", departure: Date.t(), return: nil, errors: []} %{direction: "one-way", departure: Date.t(), return: nil, errors: [:departure]} %{direction: "one-way", departure: Date.t(), return: nil, errors: [:return]} %{direction: "one-way", departure: Date.t(), return: nil, errors: [:departure, :return]} %{direction: "one-way", departure: nil, return: nil, errors: []} %{direction: "one-way", departure: nil, return: nil, errors: [:departure]} %{direction: "one-way", departure: nil, return: nil, errors: [:return]} %{direction: "one-way", departure: nil, return: nil, errors: [:departure, :return]} # two-way %{direction: "two-way", departure: Date.t(), return: Date.t(), errors: []} %{direction: "two-way", departure: Date.t(), return: Date.t(), errors: [:departure]} %{direction: "two-way", departure: Date.t(), return: Date.t(), errors: [:return]} %{direction: "two-way", departure: Date.t(), return: Date.t(), errors: [:departure, :return]} %{direction: "two-way", departure: nil, return: Date.t(), errors: []} %{direction: "two-way", departure: nil, return: Date.t(), errors: [:departure]} %{direction: "two-way", departure: nil, return: Date.t(), errors: [:return]} %{direction: "two-way", departure: nil, return: Date.t(), errors: [:departure, :return]} %{direction: "two-way", departure: Date.t(), return: nil, errors: []} %{direction: "two-way", departure: Date.t(), return: nil, errors: [:departure]} %{direction: "two-way", departure: Date.t(), return: nil, errors: [:return]} %{direction: "two-way", departure: Date.t(), return: nil, errors: [:departure, :return]} %{direction: "two-way", departure: nil, return: nil, errors: []} %{direction: "two-way", departure: nil, return: nil, errors: [:departure]} %{direction: "two-way", departure: nil, return: nil, errors: [:return]} %{direction: "two-way", departure: nil, return: nil, errors: [:departure, :return]}
103. "Please select a valid return date" %{ direction: "one-way", departure: Date.t(), return: nil, errors: [:return] }
104. "Please select a valid return date" %{ direction: "one-way", departure: Date.t(), return: nil, errors: [:return] } ▸ !
105. ONLY 6 VALID STATES! ## one-way flight # one way flight %{direction: "one-way", departure: Date.t(), return: nil, errors: []} # one way flight with departure error %{direction: "one-way", departure: nil, return: nil, errors: [:departure]} ## two-way flight # two-way flight %{direction: "two-way", departure: Date.t(), return: Date.t(), errors: []} # two-way flight with errors %{direction: "two-way", departure: nil, return: Date.t(), errors: [:departure]} %{direction: "two-way", departure: Date.t(), return: nil, errors: [:return]} %{direction: "two-way", departure: nil, return: nil, errors: [:departure, :return]}
106. ONLY 6 VALID STATES! ## one-way flight # one way flight %{direction: "one-way", departure: Date.t(), return: nil, errors: []} # one way flight with departure error %{direction: "one-way", departure: nil, return: nil, errors: [:departure]} ## two-way flight # two-way flight %{direction: "two-way", departure: Date.t(), return: Date.t(), errors: []} # two-way flight with errors %{direction: "two-way", departure: nil, return: Date.t(), errors: [:departure]} %{direction: "two-way", departure: Date.t(), return: nil, errors: [:return]} %{direction: "two-way", departure: nil, return: nil, errors: [:departure, :return]}
107. ONLY 6 VALID STATES! ## one-way flight # one way flight %{direction: "one-way", departure: Date.t(), return: nil, errors: []} # one way flight with departure error %{direction: "one-way", departure: nil, return: nil, errors: [:departure]} ## two-way flight # two-way flight %{direction: "two-way", departure: Date.t(), return: Date.t(), errors: []} # two-way flight with errors %{direction: "two-way", departure: nil, return: Date.t(), errors: [:departure]} %{direction: "two-way", departure: Date.t(), return: nil, errors: [:return]} %{direction: "two-way", departure: nil, return: nil, errors: [:departure, :return]}
108. ONLY 6 VALID STATES! ## one-way flight # one way flight %{direction: "one-way", departure: Date.t(), return: nil, errors: []} # one way flight with departure error %{direction: "one-way", departure: nil, return: nil, errors: [:departure]} ## two-way flight # two-way flight %{direction: "two-way", departure: Date.t(), return: Date.t(), errors: []} # two-way flight with errors %{direction: "two-way", departure: nil, return: Date.t(), errors: [:departure]} %{direction: "two-way", departure: Date.t(), return: nil, errors: [:return]} %{direction: "two-way", departure: nil, return: nil, errors: [:departure, :return]}
109. ONLY 6 VALID STATES! ## one-way flight # one way flight %{direction: "one-way", departure: Date.t(), return: nil, errors: []} # one way flight with departure error %{direction: "one-way", departure: nil, return: nil, errors: [:departure]} ## two-way flight # two-way flight %{direction: "two-way", departure: Date.t(), return: Date.t(), errors: []} # two-way flight with errors %{direction: "two-way", departure: nil, return: Date.t(), errors: [:departure]} %{direction: "two-way", departure: Date.t(), return: nil, errors: [:return]} %{direction: "two-way", departure: nil, return: nil, errors: [:departure, :return]}
110. INCLUDING ERRORS IN OUR DOMAIN MODEL @type date_or_error :: Date.t() | {:error, any()} @type flight_booker :: {:one_way, date_or_error} | {:two_way, date_or_error, date_or_error}
111. INCLUDING ERRORS IN OUR DOMAIN MODEL @type date_or_error :: Date.t() | {:error, any()} @type flight_booker :: {:one_way, date_or_error} | {:two_way, date_or_error, date_or_error}
112. INCLUDING ERRORS IN OUR DOMAIN MODEL @type date_or_error :: Date.t() | {:error, any()} @type flight_booker :: {:one_way, date_or_error} | {:two_way, date_or_error, date_or_error}
113. INCLUDING ERRORS IN OUR DOMAIN MODEL @type date_or_error :: Date.t() | {:error, any()} @type flight_booker :: {:one_way, date_or_error} | {:two_way, date_or_error, date_or_error}
114. INCLUDING ERRORS IN OUR DOMAIN MODEL @type date_or_error :: Date.t() | {:error, any()} @type flight_booker :: {:one_way, date_or_error} | {:two_way, date_or_error, date_or_error}
115. POSSIBLE STATES IN OUR DOMAIN MODEL # one way {:one_way, Date.t()} {:one_way, {:error, any()}} # two way {:two_way, departure: Date.t(), return: Date.t()} {:two_way, departure: {:error, any()}, return: Date.t()} {:two_way, departure: Date.t(), return: {:error, any()}} {:two_way, departure: {:error, any()}, return: {:error, any()}}
116. POSSIBLE STATES IN OUR DOMAIN MODEL # one way {:one_way, Date.t()} {:one_way, {:error, any()}} # two way {:two_way, departure: Date.t(), return: Date.t()} {:two_way, departure: {:error, any()}, return: Date.t()} {:two_way, departure: Date.t(), return: {:error, any()}} {:two_way, departure: {:error, any()}, return: {:error, any()}}
117. POSSIBLE STATES IN OUR DOMAIN MODEL # one way {:one_way, Date.t()} {:one_way, {:error, any()}} # two way {:two_way, departure: Date.t(), return: Date.t()} {:two_way, departure: {:error, any()}, return: Date.t()} {:two_way, departure: Date.t(), return: {:error, any()}} {:two_way, departure: {:error, any()}, return: {:error, any()}}
118. RENDERING COMPLEX TYPES <form phx-submit="book" phx-change="update"> <%= case @booker do %> <% {:one_way, departure} -> %> <%= select :booking, :flight_type, ["one-way", "two-way"], value: "one-way" %> <.departure_input departure={departure} /> <% {:two_way, departure, return} -> %> <%= select :booking, :flight_type, ["one-way", "two-way"], value: "two-way" %> <.departure_input departure={departure} /> <.return_input return={return} /> <% end %> <%= submit "Book" %> </form>
119. RENDERING COMPLEX TYPES <form phx-submit="book" phx-change="update"> <%= case @booker do %> <% {:one_way, departure} -> %> <%= select :booking, :flight_type, ["one-way", "two-way"], value: "one-way" %> <.departure_input departure={departure} /> <% {:two_way, departure, return} -> %> <%= select :booking, :flight_type, ["one-way", "two-way"], value: "two-way" %> <.departure_input departure={departure} /> <.return_input return={return} /> <% end %> <%= submit "Book" %> </form>
120. RENDERING COMPLEX TYPES <form phx-submit="book" phx-change="update"> <%= case @booker do %> <% {:one_way, departure} -> %> <%= select :booking, :flight_type, ["one-way", "two-way"], value: "one-way" %> <.departure_input departure={departure} /> <% {:two_way, departure, return} -> %> <%= select :booking, :flight_type, ["one-way", "two-way"], value: "two-way" %> <.departure_input departure={departure} /> <.return_input return={return} /> <% end %> <%= submit "Book" %> </form>
121. RENDERING COMPLEX TYPES <form phx-submit="book" phx-change="update"> <%= case @booker do %> <% {:one_way, departure} -> %> <%= select :booking, :flight_type, ["one-way", "two-way"], value: "one-way" %> <.departure_input departure={departure} /> <% {:two_way, departure, return} -> %> <%= select :booking, :flight_type, ["one-way", "two-way"], value: "two-way" %> <.departure_input departure={departure} /> <.return_input return={return} /> <% end %> <%= submit "Book" %> </form>
122. RENDERING COMPLEX TYPES (DEPARTURE INPUT) def departure_input(assigns) do ~H""" <%= case @departure do %> <% {:error, value} -> %> <%= text_input :booking, :departure, value: value, class: "invalid" %> <span class="invalid-feedback">is invalid</span> <% value -> %> <%= text_input :booking, :departure, value: value %> <% end %> """ end
123. RENDERING COMPLEX TYPES (DEPARTURE INPUT) def departure_input(assigns) do ~H""" <%= case @departure do %> <% {:error, value} -> %> <%= text_input :booking, :departure, value: value, class: "invalid" %> <span class="invalid-feedback">is invalid</span> <% value -> %> <%= text_input :booking, :departure, value: value %> <% end %> """ end
124. RENDERING COMPLEX TYPES (DEPARTURE INPUT) def departure_input(assigns) do ~H""" <%= case @departure do %> <% {:error, value} -> %> <%= text_input :booking, :departure, value: value, class: "invalid" %> <span class="invalid-feedback">is invalid</span> <% value -> %> <%= text_input :booking, :departure, value: value %> <% end %> """ end
125. RENDERING COMPLEX TYPES (DEPARTURE INPUT) def departure_input(assigns) do ~H""" <%= case @departure do %> <% {:error, value} -> %> <%= text_input :booking, :departure, value: value, class: "invalid" %> <span class="invalid-feedback">is invalid</span> <% value -> %> <%= text_input :booking, :departure, value: value %> <% end %> """ end
126. RENDERING COMPLEX TYPES (RETURN INPUT) def return_input(assigns) do ~H""" <%= case @return do %> <% {:error, value} -> %> <%= text_input :booking, :return, value: value, class: "invalid" %> <span class="invalid-feedback">is invalid</span> <% value -> %> <%= text_input :booking, :return, value: value %> <% end %> """ end
127. RENDERING COMPLEX TYPES (RETURN INPUT) def return_input(assigns) do ~H""" <%= case @return do %> <% {:error, value} -> %> <%= text_input :booking, :return, value: value, class: "invalid" %> <span class="invalid-feedback">is invalid</span> <% value -> %> <%= text_input :booking, :return, value: value %> <% end %> """ end
128. RENDERING COMPLEX TYPES (RETURN INPUT) def return_input(assigns) do ~H""" <%= case @return do %> <% {:error, value} -> %> <%= text_input :booking, :return, value: value, class: "invalid" %> <span class="invalid-feedback">is invalid</span> <% value -> %> <%= text_input :booking, :return, value: value %> <% end %> """ end
129. RENDERING COMPLEX TYPES (RETURN INPUT) def return_input(assigns) do ~H""" <%= case @return do %> <% {:error, value} -> %> <%= text_input :booking, :return, value: value, class: "invalid" %> <span class="invalid-feedback">is invalid</span> <% value -> %> <%= text_input :booking, :return, value: value %> <% end %> """ end
130. TRANSFORM USER INPUT (BEFORE) defp parse_params_into_booking(params) do case params do %{"flight_type" => "one-way", "departure" => departure} -> departure |> Date.from_iso8601!() |> FlightBooker.one_way() %{"flight_type" => "two-way", "departure" => departure, "return" => return} -> departure_date = departure |> Date.from_iso8601!() return_date = return |> Date.from_iso8601!() FlightBooker.two_way(departure_date, return_date) %{"flight_type" => "two-way", "departure" => departure} -> departure_date = departure |> Date.from_iso8601!() return_date = Date.utc_today() FlightBooker.two_way(departure_date, return_date) end end
131. TRANSFORM USER INPUT (BEFORE) defp parse_params_into_booking(params) do case params do %{"flight_type" => "one-way", "departure" => departure} -> departure |> Date.from_iso8601!() |> FlightBooker.one_way() %{"flight_type" => "two-way", "departure" => departure, "return" => return} -> departure_date = departure |> Date.from_iso8601!() return_date = return |> Date.from_iso8601!() FlightBooker.two_way(departure_date, return_date) %{"flight_type" => "two-way", "departure" => departure} -> departure_date = departure |> Date.from_iso8601!() return_date = Date.utc_today() FlightBooker.two_way(departure_date, return_date) end end
132. TRANSFORM USER INPUT (NOW) defp parse_params_into_booking(params) do case params do %{"flight_type" => "one-way", "departure" => departure} -> FlightBooker.one_way(departure) %{"flight_type" => "two-way", "departure" => departure, "return" => return} -> FlightBooker.two_way(departure, return) %{"flight_type" => "two-way", "departure" => departure} -> return = Date.utc_today() |> Date.to_string() FlightBooker.two_way(departure, return) end end
133. TRANSFORM USER INPUT (NOW) defp parse_params_into_booking(params) do case params do %{"flight_type" => "one-way", "departure" => departure} -> FlightBooker.one_way(departure) %{"flight_type" => "two-way", "departure" => departure, "return" => return} -> FlightBooker.two_way(departure, return) %{"flight_type" => "two-way", "departure" => departure} -> return = Date.utc_today() |> Date.to_string() FlightBooker.two_way(departure, return) end end
134. TRANSFORM USER INPUT (NOW) defp parse_params_into_booking(params) do case params do %{"flight_type" => "one-way", "departure" => departure} -> FlightBooker.one_way(departure) %{"flight_type" => "two-way", "departure" => departure, "return" => return} -> FlightBooker.two_way(departure, return) %{"flight_type" => "two-way", "departure" => departure} -> return = Date.utc_today() |> Date.to_string() FlightBooker.two_way(departure, return) end end
135. PARSING INPUT INTO OUR DOMAIN def one_way(departure_value) do departure_value |> parse_date() |> build_one_way() end def two_way(departure_value, return_value) do departure = parse_date(departure_value) return = parse_date(return_value) build_two_way(departure, return) end
136. PARSING INPUT INTO OUR DOMAIN def one_way(departure_value) do departure_value |> parse_date() |> build_one_way() end def two_way(departure_value, return_value) do departure = parse_date(departure_value) return = parse_date(return_value) build_two_way(departure, return) end
137. PARSING INPUT INTO OUR DOMAIN defp parse_date(%Date{} = date), do: date defp parse_date(string_date) when is_binary(string_date) do case Date.from_iso8601(string_date) do {:ok, date} -> date {:error, _} -> error(string_date) end end defp parse_date(value), do: error(value) defp error(value), do: {:error, value}
138. PARSING INPUT INTO OUR DOMAIN defp parse_date(%Date{} = date), do: date defp parse_date(string_date) when is_binary(string_date) do case Date.from_iso8601(string_date) do {:ok, date} -> date {:error, _} -> error(string_date) end end defp parse_date(value), do: error(value) defp error(value), do: {:error, value}
139. PARSING INPUT INTO OUR DOMAIN defp parse_date(%Date{} = date), do: date defp parse_date(string_date) when is_binary(string_date) do case Date.from_iso8601(string_date) do {:ok, date} -> date {:error, _} -> error(string_date) end end defp parse_date(value), do: error(value) defp error(value), do: {:error, value}
140. PARSING INPUT INTO OUR DOMAIN defp parse_date(%Date{} = date), do: date defp parse_date(string_date) when is_binary(string_date) do case Date.from_iso8601(string_date) do {:ok, date} -> date {:error, _} -> error(string_date) end end defp parse_date(value), do: error(value) defp error(value), do: {:error, value}
141. PARSING INPUT INTO OUR DOMAIN defp parse_date(%Date{} = date), do: date defp parse_date(string_date) when is_binary(string_date) do case Date.from_iso8601(string_date) do {:ok, date} -> date {:error, _} -> error(string_date) end end defp parse_date(value), do: error(value) defp error(value), do: {:error, value}
142. PARSING INPUT INTO OUR DOMAIN defp parse_date(%Date{} = date), do: date defp parse_date(string_date) when is_binary(string_date) do case Date.from_iso8601(string_date) do {:ok, date} -> date {:error, _} -> error(string_date) end end defp parse_date(value), do: error(value) defp error(value), do: {:error, value}
143. PARSING INPUT INTO OUR DOMAIN defp parse_date(%Date{} = date), do: date defp parse_date(string_date) when is_binary(string_date) do case Date.from_iso8601(string_date) do {:ok, date} -> date {:error, _} -> error(string_date) end end defp parse_date(value), do: error(value) defp error(value), do: {:error, value}
144. PARSING INPUT INTO OUR DOMAIN def one_way(departure_value) do departure_value |> parse_date() |> build_one_way() end def two_way(departure_value, return_value) do departure = parse_date(departure_value) return = parse_date(return_value) build_two_way(departure, return) end
145. PARSING INPUT INTO OUR DOMAIN def one_way(departure_value) do departure_value |> parse_date() |> build_one_way() end def two_way(departure_value, return_value) do departure = parse_date(departure_value) return = parse_date(return_value) build_two_way(departure, return) end
146. PARSING INPUT INTO OUR DOMAIN defp build_one_way(date) do {:one_way, date} end defp build_two_way(departure, return) do {:two_way, departure, return} end
147. 26 INVALID STATES REMOVED # one-way %{direction: "one-way", departure: Date.t(), return: Date.t(), errors: []} %{direction: "one-way", departure: Date.t(), return: Date.t(), errors: [:departure]} %{direction: "one-way", departure: Date.t(), return: Date.t(), errors: [:return]} %{direction: "one-way", departure: Date.t(), return: Date.t(), errors: [:departure, :return]} %{direction: "one-way", departure: nil, return: Date.t(), errors: []} %{direction: "one-way", departure: nil, return: Date.t(), errors: [:departure]} %{direction: "one-way", departure: nil, return: Date.t(), errors: [:return]} %{direction: "one-way", departure: nil, return: Date.t(), errors: [:departure, :return]} %{direction: "one-way", departure: Date.t(), return: nil, errors: [:departure]} %{direction: "one-way", departure: Date.t(), return: nil, errors: [:return]} %{direction: "one-way", departure: Date.t(), return: nil, errors: [:departure, :return]} %{direction: "one-way", departure: nil, return: nil, errors: []} %{direction: "one-way", departure: nil, return: nil, errors: [:return]} %{direction: "one-way", departure: nil, return: nil, errors: [:departure, :return]} # two-way %{direction: "two-way", departure: Date.t(), return: Date.t(), errors: [:departure]} %{direction: "two-way", departure: Date.t(), return: Date.t(), errors: [:return]} %{direction: "two-way", departure: Date.t(), return: Date.t(), errors: [:departure, :return]} %{direction: "two-way", departure: nil, return: Date.t(), errors: []} %{direction: "two-way", departure: nil, return: Date.t(), errors: [:return]} %{direction: "two-way", departure: nil, return: Date.t(), errors: [:departure, :return]} %{direction: "two-way", departure: Date.t(), return: nil, errors: []} %{direction: "two-way", departure: Date.t(), return: nil, errors: [:departure]} %{direction: "two-way", departure: Date.t(), return: nil, errors: [:departure, :return]} %{direction: "two-way", departure: nil, return: nil, errors: []} %{direction: "two-way", departure: nil, return: nil, errors: [:departure]} %{direction: "two-way", departure: nil, return: nil, errors: [:return]}
148. 26 INVALID STATES REMOVED
149. WE CANNOT MODEL EVERYTHING
150. WE CANNOT MODEL EVERYTHING ▸ Validate what you cannot constrain with modeling
151. VALIDATE WHAT YOU CANNOT CONSTRAIN WITH MODELING def book_trip({:two_way, departure, return}) do if Date.compare(departure, return) == :gt do {:error, "Departure cannot be after return"} else {:ok, "You have booked a two-way flight departing #{departure} and returning #{return}"} end end
152. VALIDATE WHAT YOU CANNOT CONSTRAIN WITH MODELING def book_trip({:two_way, departure, return}) do if Date.compare(departure, return) == :gt do {:error, "Departure cannot be after return"} else {:ok, "You have booked a two-way flight departing #{departure} and returning #{return}"} end end
153. VALIDATE WHAT YOU CANNOT CONSTRAIN WITH MODELING def book_trip({:two_way, departure, return}) do if Date.compare(departure, return) == :gt do {:error, "Departure cannot be after return"} else {:ok, "You have booked a two-way flight departing #{departure} and returning #{return}"} end end
154. VALIDATE WHAT YOU CANNOT CONSTRAIN WITH MODELING def book_trip({:two_way, departure, return}) do if Date.compare(departure, return) == :gt do {:error, "Departure cannot be after return"} else {:ok, "You have booked a two-way flight departing #{departure} and returning #{return}"} end end
155. !
156. WHAT ABOUT ECTO?
157. WHAT ABOUT ECTO? ▸ Well integrated with Phoenix forms
158. WHAT ABOUT ECTO? ▸ Well integrated with Phoenix forms ▸ Great casting helpers
159. WHAT ABOUT ECTO? ▸ Well integrated with Phoenix forms ▸ Great casting helpers ▸ Great validation helpers
160. WHAT ABOUT ECTO? ▸ Well integrated with Phoenix forms ▸ Great casting helpers ▸ Great validation helpers ▸ Use schemaless changesets as an anti-corruption layer
161. WHAT ABOUT ECTO? Use Ecto as much as you can
162. WHAT ABOUT ECTO? ! Ecto shines with maps (and structs)
163. COMBINE SUM TYPES WITH ECTO CHANGESETS
164. COMBINE SUM TYPES WITH ECTO CHANGESETS @type flight_booker :: {:one_way, date_or_error} | {:two_way, date_or_error, date_or_error}
165. COMBINE SUM TYPES WITH ECTO CHANGESETS @type flight_booker :: {:one_way, date_or_error} | {:two_way, date_or_error, date_or_error}
166. COMBINE SUM TYPES WITH ECTO CHANGESETS @type flight_booker :: {:one_way, Ecto.Changeset.t()} | {:two_way, Ecto.Changeset.t()}
167. USE ECTO'S CASTING & ERROR GENERATION def one_way(departure_value) do departure_value |> parse_date() |> build_one_way() end def two_way(departure_value, return_value) do departure = parse_date(departure_value) return = parse_date(return_value) build_two_way(departure, return) end
168. USE ECTO'S CASTING & ERROR GENERATION def one_way(departure_value) do departure_value |> parse_date() |> build_one_way() end def two_way(departure_value, return_value) do departure = parse_date(departure_value) return = parse_date(return_value) build_two_way(departure, return) end
169. USE ECTO'S CASTING & ERROR GENERATION def one_way(departure_value) do %OneWay{} |> OneWay.changeset(%{departure: departure_value}) |> build_one_way() end def two_way(departure_value, return_value) do %TwoWay{} |> TwoWay.changeset(%{departure: departure_value, return: return_value}) |> build_two_way() end
170. USE ECTO'S CASTING & ERROR GENERATION def one_way(departure_value) do %OneWay{} |> OneWay.changeset(%{departure: departure_value}) |> build_one_way() end def two_way(departure_value, return_value) do %TwoWay{} |> TwoWay.changeset(%{departure: departure_value, return: return_value}) |> build_two_way() end
171. RENDERING COMPLEX TYPES <%= case @booker do %> <% {:one_way, changeset} -> %> <%= select :booker, :flight_type, ["one-way", "two-way"], phx_click: "change-flight-type", value: "one-way", id: "flight-type" %> <.form let={f} for={changeset} phx-submit="book" phx-change="update"> <%= text_input f, :departure %> <%= error_tag f, :departure %> <%= submit "Book", id: "book-flight" %> </.form> <% {:two_way, changeset} -> %> <%= select :booker, :flight_type, ["one-way", "two-way"], phx_click: "change-flight-type", value: "two-way", id: "flight-type" %> <.form let={f} for={changeset} phx-submit="book" phx-change="update"> <%= text_input f, :departure %> <%= error_tag f, :departure %> <%= text_input f, :return %> <%= error_tag f, :return %> <%= submit "Book", id: "book-flight" %> </.form> <% end %>
172. RENDERING COMPLEX TYPES <%= case @booker do %> <% {:one_way, changeset} -> %> <%= select :booker, :flight_type, ["one-way", "two-way"], phx_click: "change-flight-type", value: "one-way", id: "flight-type" %> <.form let={f} for={changeset} phx-submit="book" phx-change="update"> <%= text_input f, :departure %> <%= error_tag f, :departure %> <%= submit "Book", id: "book-flight" %> </.form> <% {:two_way, changeset} -> %> <%= select :booker, :flight_type, ["one-way", "two-way"], phx_click: "change-flight-type", value: "two-way", id: "flight-type" %> <.form let={f} for={changeset} phx-submit="book" phx-change="update"> <%= text_input f, :departure %> <%= error_tag f, :departure %> <%= text_input f, :return %> <%= error_tag f, :return %> <%= submit "Book", id: "book-flight" %> </.form> <% end %>
173. RENDERING COMPLEX TYPES <%= case @booker do %> <% {:one_way, changeset} -> %> <%= select :booker, :flight_type, ["one-way", "two-way"], phx_click: "change-flight-type", value: "one-way", id: "flight-type" %> <.form let={f} for={changeset} phx-submit="book" phx-change="update"> <%= text_input f, :departure %> <%= error_tag f, :departure %> <%= submit "Book", id: "book-flight" %> </.form> <% {:two_way, changeset} -> %> <%= select :booker, :flight_type, ["one-way", "two-way"], phx_click: "change-flight-type", value: "two-way", id: "flight-type" %> <.form let={f} for={changeset} phx-submit="book" phx-change="update"> <%= text_input f, :departure %> <%= error_tag f, :departure %> <%= text_input f, :return %> <%= error_tag f, :return %> <%= submit "Book", id: "book-flight" %> </.form> <% end %>
174. RENDERING COMPLEX TYPES <%= case @booker do %> <% {:one_way, changeset} -> %> <%= select :booker, :flight_type, ["one-way", "two-way"], phx_click: "change-flight-type", value: "one-way", id: "flight-type" %> <.form let={f} for={changeset} phx-submit="book" phx-change="update"> <%= text_input f, :departure %> <%= error_tag f, :departure %> <%= submit "Book", id: "book-flight" %> </.form> <% {:two_way, changeset} -> %> <%= select :booker, :flight_type, ["one-way", "two-way"], phx_click: "change-flight-type", value: "two-way", id: "flight-type" %> <.form let={f} for={changeset} phx-submit="book" phx-change="update"> <%= text_input f, :departure %> <%= error_tag f, :departure %> <%= text_input f, :return %> <%= error_tag f, :return %> <%= submit "Book", id: "book-flight" %> </.form> <% end %>
175. RENDERING COMPLEX TYPES <%= case @booker do %> <% {:one_way, changeset} -> %> <%= select :booker, :flight_type, ["one-way", "two-way"], phx_click: "change-flight-type", value: "one-way", id: "flight-type" %> <.form let={f} for={changeset} phx-submit="book" phx-change="update"> <%= text_input f, :departure %> <%= error_tag f, :departure %> <%= submit "Book", id: "book-flight" %> </.form> <% {:two_way, changeset} -> %> <%= select :booker, :flight_type, ["one-way", "two-way"], phx_click: "change-flight-type", value: "two-way", id: "flight-type" %> <.form let={f} for={changeset} phx-submit="book" phx-change="update"> <%= text_input f, :departure %> <%= error_tag f, :departure %> <%= text_input f, :return %> <%= error_tag f, :return %> <%= submit "Book", id: "book-flight" %> </.form> <% end %>
176. RENDERING COMPLEX TYPES <%= case @booker do %> <% {:one_way, changeset} -> %> <%= select :booker, :flight_type, ["one-way", "two-way"], phx_click: "change-flight-type", value: "one-way", id: "flight-type" %> <.form let={f} for={changeset} phx-submit="book" phx-change="update"> <%= text_input f, :departure %> <%= error_tag f, :departure %> <%= submit "Book", id: "book-flight" %> </.form> <% {:two_way, changeset} -> %> <%= select :booker, :flight_type, ["one-way", "two-way"], phx_click: "change-flight-type", value: "two-way", id: "flight-type" %> <.form let={f} for={changeset} phx-submit="book" phx-change="update"> <%= text_input f, :departure %> <%= error_tag f, :departure %> <%= text_input f, :return %> <%= error_tag f, :return %> <%= submit "Book", id: "book-flight" %> </.form> <% end %>
177. RENDERING COMPLEX TYPES <%= case @booker do %> <% {:one_way, changeset} -> %> <%= select :booker, :flight_type, ["one-way", "two-way"], phx_click: "change-flight-type", value: "one-way", id: "flight-type" %> <.form let={f} for={changeset} phx-submit="book" phx-change="update"> <%= text_input f, :departure %> <%= error_tag f, :departure %> <%= submit "Book", id: "book-flight" %> </.form> <% {:two_way, changeset} -> %> <%= select :booker, :flight_type, ["one-way", "two-way"], phx_click: "change-flight-type", value: "two-way", id: "flight-type" %> <.form let={f} for={changeset} phx-submit="book" phx-change="update"> <%= text_input f, :departure %> <%= error_tag f, :departure %> <%= text_input f, :return %> <%= error_tag f, :return %> <%= submit "Book", id: "book-flight" %> </.form> <% end %>
178. RENDERING COMPLEX TYPES <%= case @booker do %> <% {:one_way, changeset} -> %> <button type="button" phx-click="change-flight-type" value="two-way">Two-way</button> <.form let={f} for={changeset} phx-submit="book" phx-change="update"> <%= text_input f, :departure %> <%= error_tag f, :departure %> <%= submit "Book", id: "book-flight" %> </.form> <% {:two_way, changeset} -> %> <button type="button" phx-click="change-flight-type" value="one-way">One-way</button> <.form let={f} for={changeset} phx-submit="book" phx-change="update"> <%= text_input f, :departure %> <%= error_tag f, :departure %> <%= text_input f, :return %> <%= error_tag f, :return %> <%= submit "Book", id: "book-flight" %> </.form> <% end %>
179. HANDLE CHANGE OF STATE def handle_event("change-flight-type", %{"value" => "one-way"}, socket) do date = Date.utc_today() booker = FlightBooker.one_way(date) socket |> assign(:booker, booker) |> noreply() end def handle_event("change-flight-type", %{"value" => "two-way"}, socket) do date = Date.utc_today() booker = FlightBooker.two_way(date, date) socket |> assign(:booker, booker) |> noreply() end
180. HANDLE CHANGE OF STATE def handle_event("change-flight-type", %{"value" => "one-way"}, socket) do date = Date.utc_today() booker = FlightBooker.one_way(date) socket |> assign(:booker, booker) |> noreply() end def handle_event("change-flight-type", %{"value" => "two-way"}, socket) do date = Date.utc_today() booker = FlightBooker.two_way(date, date) socket |> assign(:booker, booker) |> noreply() end
181. HANDLE CHANGE OF STATE def handle_event("change-flight-type", %{"value" => "one-way"}, socket) do date = Date.utc_today() booker = FlightBooker.one_way(date) socket |> assign(:booker, booker) |> noreply() end def handle_event("change-flight-type", %{"value" => "two-way"}, socket) do date = Date.utc_today() booker = FlightBooker.two_way(date, date) socket |> assign(:booker, booker) |> noreply() end
182. HANDLE CHANGE OF STATE def handle_event("change-flight-type", %{"value" => "one-way"}, socket) do date = Date.utc_today() booker = FlightBooker.one_way(date) socket |> assign(:booker, booker) |> noreply() end def handle_event("change-flight-type", %{"value" => "two-way"}, socket) do date = Date.utc_today() booker = FlightBooker.two_way(date, date) socket |> assign(:booker, booker) |> noreply() end
183. HANDLE CHANGE OF STATE def handle_event("change-flight-type", %{"value" => "one-way"}, socket) do date = Date.utc_today() booker = FlightBooker.one_way(date) socket |> assign(:booker, booker) |> noreply() end def handle_event("change-flight-type", %{"value" => "two-way"}, socket) do date = Date.utc_today() booker = FlightBooker.two_way(date, date) socket |> assign(:booker, booker) |> noreply() end
184. HANDLE FORMS def handle_event("update", %{"one_way" => params}, socket) do %{"departure" => departure} = params booker = FlightBooker.one_way(departure) socket |> assign(:booker, booker) |> noreply() end def handle_event("update", %{"two_way" => params}, socket) do %{"departure" => departure, "return" => return} = params booker = FlightBooker.two_way(departure, return) socket |> assign(:booker, booker) |> noreply() end
185. HANDLE FORMS def handle_event("update", %{"one_way" => params}, socket) do %{"departure" => departure} = params booker = FlightBooker.one_way(departure) socket |> assign(:booker, booker) |> noreply() end def handle_event("update", %{"two_way" => params}, socket) do %{"departure" => departure, "return" => return} = params booker = FlightBooker.two_way(departure, return) socket |> assign(:booker, booker) |> noreply() end
186. HANDLE FORMS def handle_event("update", %{"one_way" => params}, socket) do %{"departure" => departure} = params booker = FlightBooker.one_way(departure) socket |> assign(:booker, booker) |> noreply() end def handle_event("update", %{"two_way" => params}, socket) do %{"departure" => departure, "return" => return} = params booker = FlightBooker.two_way(departure, return) socket |> assign(:booker, booker) |> noreply() end
187. HANDLE FORMS def handle_event("update", %{"one_way" => params}, socket) do %{"departure" => departure} = params booker = FlightBooker.one_way(departure) socket |> assign(:booker, booker) |> noreply() end def handle_event("update", %{"two_way" => params}, socket) do %{"departure" => departure, "return" => return} = params booker = FlightBooker.two_way(departure, return) socket |> assign(:booker, booker) |> noreply() end
188. HANDLE FORMS def handle_event("update", %{"one_way" => params}, socket) do %{"departure" => departure} = params booker = FlightBooker.one_way(departure) socket |> assign(:booker, booker) |> noreply() end def handle_event("update", %{"two_way" => params}, socket) do %{"departure" => departure, "return" => return} = params booker = FlightBooker.two_way(departure, return) socket |> assign(:booker, booker) |> noreply() end
189. ! EXPLORATION NOTES
190. ! EXPLORATION NOTES ▸ Model your domain to remove invalid states
191. ! EXPLORATION NOTES ▸ Model your domain to remove invalid states ▸ ! Render complex types Declaratively & Exhaustively
192. ! EXPLORATION NOTES ▸ Model your domain to remove invalid states ▸ ! Render complex types Declaratively & Exhaustively ▸ Parse raw ⚠ unsafe values into your domain values
193. ! EXPLORATION NOTES ▸ Model your domain to remove invalid states ▸ ! Render complex types Declaratively & Exhaustively ▸ Parse raw ⚠ unsafe values into your domain values ▸ ✅ Validate what you cannot constrain
194. ! EXPLORATION NOTES ▸ Model your domain to remove invalid states ▸ ! Render complex types Declaratively & Exhaustively ▸ Parse raw ⚠ unsafe values into your domain values ▸ ✅ Validate what you cannot constrain ▸ Combine powers with Ecto $ when dealing with maps
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