How to define Macro for a new Type?

[dimitarvp]

@Fl4m3Ph03n1x

  def name?({:name, val}) when is_binary(val), do: true

Sorry to comment on the previous idea – but that’s way too global. In a moderately big project you can have 5 different kinds of names. So to implement this properly you’d likely have to scope this somehow e.g. with module names (which are also atoms as you know):

defmodule MyApp.Types.Address.Name do
  def name?({__MODULE__, val}) when is_binary(val), do: true

In many languages, internally types get all sorts of fancy prefixes. That’s important. You don’t want only one Name to be ever allowed in your project.

@Fl4m3Ph03n1x

  def is_type?({type, _data}, new_type) when type == new_type, do: true
  def is_type?(_data, _new_type), do: false

Elixir offers an even neater way of doing this:

def is_type?({type, _data}, type), do: true # note the repeated `type` variable
def is_type?(_data, _new_type), do: false

Examples:

is_type?({:x, "something"}, :x} # returns true
is_type?({:x, "something"}, :y} # returns false