Behaviour for custom event field types.

Event declarations use type identifiers to describe the shape of event data. Built-in atomic types (:number, :string, :boolean, :any) are handled implicitly. Module types implement this behaviour to provide custom parsing from wire-format values to Elixir types.

Built-in atomic types

These types pass through with validation only (no transformation):

• :number -- integer or float
• :string -- binary
• :boolean -- true or false
• :any -- any term, no validation

Module types

Any module that implements this behaviour can be used as a type in event declarations. The module must define parse/1, which transforms a wire-format value into an Elixir value.

Example

defmodule MyApp.Direction do
  @behaviour Plushie.EventType

  @impl true
  def parse("up"), do: {:ok, :up}
  def parse("down"), do: {:ok, :down}
  def parse("left"), do: {:ok, :left}
  def parse("right"), do: {:ok, :right}
  def parse(_), do: :error
end

Then in an event declaration:

event :swipe, data: [direction: MyApp.Direction]