How to pass a member function/delegate into a mixin template?
"岩倉 澪" via Digitalmars-d-learn
digitalmars-d-learn at puremagic.com
Mon Sep 15 06:50:20 PDT 2014
Hi all,
I've been reading D Cookbook, in which the author recommends the
use of mixin templates to essentially hold boilerplate code for
classes (page 28). Referencing TDPL reaffirms this strategy. With
this design choice in mind, I would like to be able to use a
mixin template that creates a slot for me (as in signals & slots)
and provides a constructor that connects it to the signal.
The closest I have come is in the simplified example given below:
EventHandler event_handler;
class EventHandler{
...
mixin std.signals.Signal!Event;
...
}
mixin template EventListener(void delegate(Event) slot){
private this()
in{ assert(event_handler); }
body{ event_handler.connect(&eventListener); }
private void eventListener(Event e){ slot(e); }
}
class Foo{
mixin EventListener!((e){ ... });
}
Sadly, this code does not compile.
My understanding (and correct me if I'm wrong) is that this does
not compile because I cannot create such a delegate, as the scope
that it would be in is not available at compile time (it would be
objects instantiated from class Foo in this example).
One strategy that works is to not pass anything to the mixin
template, and have the mixin template use a function that is
presumed to exist. It is then the duty of the class writer to
make sure a function of the correct name and signature exists if
they use this mixin. However, I worry that this is poor/brittle
design.
What is the best approach to achieve this?
Thanks, Mio
More information about the Digitalmars-d-learn
mailing list