I’d think that you’d probably want to create a MyApp.Foo.from_foo_resource/1 to encapsulate the knowledge of how to transform a %DB.FooResource{} into a %MyApp.Foo{} rather than potentially hard-coding that knowledge in multiple places. It might look something like:

defmodule MyApp.Foo do
  defstruct [:name]
  
  def from_foo_resource(%DB.FooResource{} = foo_resource) do
    struct(MyApp.Foo, Map.from_struct(foo_resource))
  end
end

Then if you have a list of %DB.FooResource{} you can do

resource_list = [%DB.FooResource{name: "a"}, %DB.FooResource{name: "b"}]
foo_list = Enum.map(resource_list, &MyApp.Foo.from_foo_resource/1)

Although if all you have is a one-to-one mapping this entire approach sounds like it is overkill (but it is an interesting experiment). I’d imagine if you’re combining multiple DB resources into one representation then something like this definitely makes sense. Or if you’re doing some type of CQRS system.

Another way would be using struct(MyApp.Foo, Map.from_struct(db_struct))

@matiso we’re doing something similar with an umbrella app.

Here’s what we came up with.

defmodule Context.Primary.Helpers.Entity do
  def new(nil, _entity) do
    nil
  end

  def new(%_{} = struct, entity) do
    struct
    |> Map.from_struct()
    |> new(entity)
  end

  def new(data, entity) do
    struct(entity, data)
  end
end

Pretty straightforward. This does break down when you need to compose something from multiple sources.