Example of using an Effect to add scope to nested effects

foolin.py

from __future__ import print_function

from characteristic import attributes
from effect import Effect, perform, ConstantIntent, base_dispatcher, sync_performer
from effect.dispatcher import TypeDispatcher, ComposedDispatcher


@attributes(['name'])
class MyThing(object):
    """Intent."""
    pass


@attributes(['scope', 'effect'])
class MyDecorator(object):
    """Intent which decorates another Effect."""
    pass



def effect_to_box(eff, box):
    return eff.on(box.succeed, box.fail)


def perform_decorator(dispatcher, decorator, box):
    print("performing a", decorator)
    def scoped_performer(innerdisp, mything, innerbox):
        print("performing", mything, "in scope", decorator.scope)
        innerbox.succeed(decorator.scope + "." + mything.name)
    new_disp = ComposedDispatcher([
        TypeDispatcher({MyThing: scoped_performer}),
        dispatcher])
    perform(new_disp, effect_to_box(decorator.effect, box))


td = TypeDispatcher({MyDecorator: perform_decorator})

disp = ComposedDispatcher([td, base_dispatcher])

eff = Effect(
    MyDecorator(
        scope='a',
        effect=Effect(
            MyThing(name='foo')
        ).on(
            lambda r: Effect(
                MyThing(name='bar')
            ).on(
                lambda r2: (r, r2)
            )
        )
    )
).on(print)


perform(disp, eff)