DoubleDown.Contract.Dispatch.StubHandler behaviour (double_down v0.47.2)

Behaviour for stateless stub handler modules.

Implement this behaviour to make a stateless stub usable by module name in DoubleDown.Double.stub/2..4:

# Instead of:
Double.stub(Repo, Repo.Stub.new())

# Write:
Double.stub(Repo, Repo.Stub)

# With a fallback function:
Double.stub(Repo, Repo.Stub, fn :all, [User] -> [] end)

Callbacks

new/2 — build a 2-arity dispatch function from a fallback function and options. The returned function has the signature fn operation, args -> result end.

Example

defmodule MyApp.TestStore do
  @behaviour DoubleDown.Contract.Dispatch.StubHandler

  @impl true
  def new(fallback_fn, _opts) do
    fn operation, args ->
      case {operation, args} do
        {:get, [id]} -> %{id: id}
        _ when is_function(fallback_fn) -> fallback_fn.(operation, args)
        _ -> raise "unhandled"
      end
    end
  end
end

Summary

Callbacks

new(fallback_fn, opts)

Build a 2-arity dispatch function from a fallback function and options.

Callbacks

new(fallback_fn, opts)

@callback new(
  fallback_fn :: (atom(), [term()] -> term()) | nil,
  opts :: keyword()
) :: (atom(), [term()] -> term())

Build a 2-arity dispatch function from a fallback function and options.

fallback_fn — an optional 2-arity function (operation, args) -> result for operations the stub doesn't handle directly. nil if not provided.
opts — additional options for configuring the stub.

Returns a 2-arity function fn operation, args -> result end suitable for use as a Double.stub function fallback.