68 lines
1.7 KiB
Elixir
68 lines
1.7 KiB
Elixir
defmodule Structs do
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use Koans
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@intro "Structs"
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defmodule Person do
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defstruct [:name, :age]
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end
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koan "Structs are defined and named after a module" do
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person = %Person{}
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assert person == ___
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end
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koan "Unless previously defined, fields begin as nil" do
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nobody = %Person{}
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assert nobody.age == ___
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end
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koan "You can pass initial values to structs" do
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joe = %Person{name: "Joe", age: 23}
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assert joe.name == ___
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end
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koan "Update fields with the cons '|' operator" do
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joe = %Person{name: "Joe", age: 23}
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older = %{joe | age: joe.age + 10}
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assert older.age == ___
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end
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defmodule Plane do
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defstruct passengers: 0, maker: :boeing
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end
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def plane?(%Plane{}), do: true
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def plane?(_), do: false
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koan "Or onto the type of the struct itself" do
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assert plane?(%Plane{passengers: 417, maker: :boeing}) == ___
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assert plane?(%Person{}) == ___
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end
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koan "Struct can be treated like maps" do
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silvia = %Person{age: 22, name: "Silvia"}
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assert Map.fetch(silvia, :age) == ___
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end
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defmodule Airline do
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defstruct plane: %Plane{}, name: "Southwest"
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end
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koan "Use the put_in macro to replace a nested value" do
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airline = %Airline{plane: %Plane{maker: :boeing}}
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assert put_in(airline.plane.maker, :airbus) == ___
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end
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koan "Use the update_in macro to modify a nested value" do
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airline = %Airline{plane: %Plane{maker: :boeing, passengers: 200}}
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assert update_in(airline.plane.passengers, &(&1 + 2)) == ___
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end
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koan "Use the put_in macro with atoms to replace a nested value in a non-struct" do
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airline = %{plane: %{maker: :boeing}, name: "Southwest"}
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assert put_in(airline[:plane][:maker], :cessna) == ___
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end
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end
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