struct - 强制执行结构中的所有键

Question

如何在不需要复制所有键的情况下强制执行结构中的所有键？为了澄清，我想干这个:

defmodule Ticket do
  @enforce_keys [:origin, :destination, :price]
  defstruct [:origin, :destination, :price]
end

我可以使用其他变量:

defmodule Ticket do
  struct_keys = [:origin, :destination, :price]
  @enforce_keys struct_keys
  defstruct struct_keys
end

它工作正常，但看起来很吵。有没有更好的方法？

Answer 1

您可以通过@enforce_keys至defstruct自从 @enforce_keys只是一个普通的模块属性:

defmodule Ticket do
  @enforce_keys [:origin, :destination, :price]
  defstruct @enforce_keys
end

iex(1)> defmodule Ticket do
...(1)>   @enforce_keys [:origin, :destination, :price]
...(1)>   defstruct @enforce_keys
...(1)> end
iex(2)> %Ticket{}
** (ArgumentError) the following keys must also be given when building struct Ticket: [:origin, :destination, :price]
    expanding struct: Ticket.__struct__/1
    iex:2: (file)