Re: How to pass a member function/delegate into a mixin template?
On Monday, 15 September 2014 at 21:37:50 UTC, John Colvin wrote: would this work for you? "alias" is the usual way of taking a function as a template parameter. mixin template EventListener(alias slot) Ah, thanks for the help! That works great. :)
Re: How to pass a member function/delegate into a mixin template?
On Monday, 15 September 2014 at 13:50:22 UTC, 岩倉 澪 wrote:
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
would this work for you? "alias" is the usual way of taking a
function as a template parameter.
mixin template EventListener(alias slot)
How to pass a member function/delegate into a mixin template?
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
