It's certainly not an obvious syntax, but it "casts" the first argument into a provider of the interface, defaulting to the second argument if this is not possible.
For example, if `parent` isn't a provider of `IServiceCollection`, but there's an adapter registered to covert to `IServiceCollection` from `type(parent)`, then that adapter will be called. If there's no such adapter, the cast will return `parent`. Dustin On Mon, May 26, 2014 at 8:27 AM, Jonas Brunsgaard <jonas.brunsga...@gmail.com> wrote: > Hello all > > Will someone explain to me what happens when you call an Interface with > arguments, and why the same argument twice? > > > > My problem is to understand the semantics of the line > > parent = IServiceCollection(parent, parent) > > > > part of > > def setServiceParent(self, parent): > > if self.parent is not None: > > self.disownServiceParent() > parent = IServiceCollection(parent, parent) > > self.parent = parent > self.parent.addService(self) > > > > in twisted.application.service > > Thanks in advance. > > > _______________________________________________ > Twisted-Python mailing list > Twisted-Python@twistedmatrix.com > http://twistedmatrix.com/cgi-bin/mailman/listinfo/twisted-python > _______________________________________________ Twisted-Python mailing list Twisted-Python@twistedmatrix.com http://twistedmatrix.com/cgi-bin/mailman/listinfo/twisted-python
