Practical tips about with (in Elixir)

Presented at October 2018 meetup of Elixir Sydney
https://www.meetup.com/sydney-ex/events/kznqrpyxnbfb/

1. Practical tips about with by Qing Wu
2. Why {:ok, result} | {:error, reason}
3. Examples HTTPoison.post(url, body, headers) Poison.decode(response) Repo.create(User, attributes)
4. conditionals case function1() do {:ok, result} -> ... {:ok, "all good"} {:error, reason} -> ... {:error, reason} end
5. nested conditionals case function1() do {:ok, result1} -> case function2() do {:ok, result2} -> ... {:ok, "all good"} {:error, reason2} -> ... {:error, reason2} end {:error, reason1} -> ... {:error, reason1} end
6. use with ☺ with {:ok, result} <- function1() do ... end # or with {:ok, result} <- function1() do ... else {:error, reason} -> ... {:error, reason} end
7. ! with {:ok, result1} <- function1(), {:ok, result2} <- function2() do ... else {:error, reason} -> ... {:error, reason} end
8. Watch out ! {:ok, result} = function1() ...
9. else in with ! with {:ok, result} <- function1() do ... else {:error, reason} -> {:error, reason} end
10. Be careful ❗ with {:ok, result} <- function1() do ... else {:error, :specific_error} -> ... end
11. Have a match all clause ! with {:ok, result} <- function1() do ... else {:error, :specific_error} -> ... {:error, "function1 failed because ..."} {:error, reason} -> {:error, reason} end
12. Do NOT abuse with ! with result <- function1() do ... end
13. For more details $ iex iex(1)> h with
14. Takeaway with is your friend, use it wisely