[Twisted-Python] A Python metaclass for Twisted allowing __init__ to return a Deferred

Esteve Fernandez esteve at sindominio.net
Mon Nov 3 09:03:42 EST 2008

On Monday 03 November 2008 14:53:24 Esteve Fernandez wrote:
> On Monday 03 November 2008 14:11:05 Terry Jones wrote:
> > >>>>> "Esteve" == Esteve Fernandez <esteve at sindominio.net> writes:
> >
> > Esteve> I'm going to jump in. How about this:
> >
> > That's nice. But you've coupled the args to aFuncReturningADeferred and
> > what it's Deferred ends up returning to the args for __init__ of the
> > class.
> Yep, that's what I meant. I wanted to show how to pass an argument to Foo,
> which will be used to call a function (that may take a considerable amount
> of time) and whose return value will be stored in a Foo instance.

Alternatively a function would suffice:

from twisted.internet import defer, reactor

def aFuncReturningADeferred(value):
    d = defer.Deferred()
    reactor.callLater(5, d.callback, value[::-1])
    return d

class SimpleFoo(object):

    def __init__(self, value):
        self.value = value

def printFoo(obj):
    print obj.value

def FooFactory(value):
    return aFuncReturningADeferred(value).addCallback(SimpleFoo)

d = FooFactory("Some value")


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