Giving access to Access

Take a quick glance at 5 cool ways to work with your data thanks to Elixir’s Access behaviour

Transcript

1. Giving access to Access 5 cool ways to work with your data thanks to Elixir’s Access behaviour
2. What is Access? • A behaviour that allows access to data structure keys • Supports keywords, maps, structs • Bracket Syntax ◦ Data[:key] ◦ Keywords and Maps ◦ Returns nil • Dot Syntax ◦ Data.key ◦ Maps and Structs ◦ Raises error
3. Callbacks • fetch(data, key) ◦ Returns tuple {ok, value} or :error • get_and_update(data, key, function) ◦ Returns tuple with old value and new data • pop(data, key) ◦ Returns tuple with old value and new data or default
5. 5 Cool Access Functions
6. 1. Access.get(container, key, default \\ nil) • Returns the value of given key • Is the reason we have bracket notation • Used in Kernel macros such as get_in • artists["beyonce knowles"] • Access.get(artists, "beyonce knowles") ◦ => %{ age: 37, songs: [ %{genre: "bounce", title: "formation"}, %{genre: "r&b", title: "beautiful liar"} ], stage_name: "beyonce” } • Artists[“the strokes”] ◦ => nil • Access.get(artists, "the strokes", %{stage_name: "the strokes"}) ◦ => %{stage_name: "the strokes"}
7. Access.key(key, default \\ nil) • Returns a function • Purpose of the function is to access the value for the given key • put_in(artists, [Access.key("natalie", %{}), Access.key(:age)], 25) ◦ => %{ age: 37, songs: [ %{genre: "bounce", title: "formation"}, %{genre: "r&b", title: "beautiful liar"} ], stage_name: "beyonce” , "natalie" => %{age: 25} }
8. Access.all( ) • Returns function that accesses all elements in a list • get_in(artists, ["beyonce knowles", :songs, Access.all, :genre]) ◦ => ["bounce", "r&b"]
9. Access.filter(function) • Returns a function that can access elements matching given guard • get_in(artists, ["elvis aaron presley",:songs, Access.filter(&(&1.genre == "classic rock")), :title]) ◦ =>[“always on my mind”]
10. Access.at(index) • Returns a function that access given list index • put_in(artists, ["elvis aaron presley", :songs, Access.at(1), :title], "brand new tunes") ◦ => %{beyone map…,%{ age: nil, songs: [ %{genre: "pop", title: "can't help falling in love"}, %{genre: "classic rock", title: "brand new tunes"}], stage_name: "elvis” }}
11. Recap Access.get => returns value for provided key Access.key => returns function to access provided key Access.all => returns function that accesses all elements in a list Access.filter => returns function that accesses specific elements in a list Access.at => returns function that accesses particular element in list