DoubleDown.Contract.Dispatch.StatelessHandler behaviour (double_down v0.56.1)

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Behaviour for stateless stub handler modules.

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

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

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

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

Callbacks

  • new/2 — build a 3-arity dispatch function from a fallback function and options. The returned function has the signature fn contract, operation, args -> result end.

Example

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

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

Summary

Callbacks

new(fallback_fn, opts)

Build a 3-arity dispatch function from a fallback function and options.

Callbacks

new(fallback_fn, opts)

@callback new(
  fallback_fn :: DoubleDown.Contract.Dispatch.Types.stateless_fun() | nil,
  opts :: keyword()
) :: DoubleDown.Contract.Dispatch.Types.stateless_fun()

Build a 3-arity dispatch function from a fallback function and options.

  • fallback_fn — an optional 3-arity function (contract, operation, args) -> result for operations the stub doesn't handle directly. nil if not provided.
  • opts — additional options for configuring the stub.

Returns a 3-arity function fn contract, operation, args -> result end suitable for use as a Double.fallback function fallback.