Skuld.Comp.IInstall behaviour (skuld v0.2.3)

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Behaviour for effects supporting handler installation via catch clauses.

This enables bare module patterns in catch clauses to install handlers:

comp do
  x <- State.get()
  x * 2
catch
  State -> 0   # calls State.__handle__(comp, 0)
end

Example

defmodule State do
  @behaviour Skuld.Comp.IInstall

  @impl Skuld.Comp.IInstall
  def __handle__(comp, initial), do: with_handler(comp, initial)
end

Config Interpretation

Effects can accept different config shapes:

# Simple value
def __handle__(comp, initial), do: with_handler(comp, initial)

# Tuple with options
def __handle__(comp, {initial, opts}), do: with_handler(comp, initial, opts)

# Keyword options
def __handle__(comp, opts) when is_list(opts), do: with_handler(comp, opts)

# Ignored config (e.g., Throw just needs to be installed)
def __handle__(comp, _config), do: with_handler(comp)

See Also

Summary

Callbacks

__handle__(comp, config)

Install a handler for this effect, wrapping the computation.

Callbacks

__handle__(comp, config)

@callback __handle__(
  comp :: Skuld.Comp.Types.computation(),
  config :: term()
) :: Skuld.Comp.Types.computation()

Install a handler for this effect, wrapping the computation.

The config term is effect-specific. Effects interpret it flexibly:

  • State.__handle__(comp, initial) - initial state value
  • Reader.__handle__(comp, env_value) - reader environment
  • Throw.__handle__(comp, _) - ignores config
  • Fresh.__handle__(comp, :uuid7) - handler variant selector