Declare the struct with use Pyc, definition: ... and get helper macros
to deal with the struct alongside the validation of updates for free.
Validation of updates works for all injected MyStruct.put/3 functions that
basically substitute the generic Map.put/3 as well as for Collectable.into/1
automatically implemented for the struct defined that way.
All functions declared with defmethod/3 get this local variable as well as
the bunch of local variables for all the keys of the struct.
Easy monadic chaining is possible with generic pipe operator.
defmodule MyStruct do
use Pyc,
definition: [foo: 42, bar: %{}, baz: []],
constraints: [%{matches: %{foo: 42, bar: ~Q[bar]}, guards: %{check_bar: "is_map(bar)"}}]
defmethod :foo!, [value] when foo < 100 and length(baz) > 0 do
%__MODULE__{this | foo: value, baz: [42 | baz]}
end
end
iex> %MyStruct{}
...> |> MyStruct.put(:baz, 42)
...> |> IO.inspect(label: "1st put")
...> |> MyStruct.put(:baz, [])
...> |> IO.inspect(label: "2nd put")
...> |> MyStruct.put(:bar, 42)
...> |> IO.inspect(label: "3rd put")
#⇒ 1st put: %MyStruct{bar: %{}, baz: 42, foo: 42}
# 2nd put: %MyStruct{bar: %{}, baz: [], foo: 42}
# 3rd put: {:error, %MyStruct{bar: 42, baz: [], foo: 42}}
iex> Enum.into([bar: %{zzz: nil}, baz: "¡Hola!"], %MyStruct)
#⇒ %MyStruct{bar: %{zzz: nil}, baz: "¡Hola!", foo: 42}
iex> Enum.into([bar: 42], %MyStruct)
#⇒ {:error, %MyStruct{bar: 42, baz: [], foo: 42}}def deps do
[
{:pyc, "~> 0.1.0"}
]
end