Re: [Boost-users] [RFC] Signals bound to phoenix functions

24 Jun 2010

      Stephan,

as I stated before in the [] you need to have a function object which is
called when the if_-condition is evaluated. It should not be a function
call, returning a non-function object!
Replacing Line 148 with:

return n_signal.connect( if_( CallingBack ) [m_signal_callback]);

will compile. If you need more complex szenario you need to make a composite
function object, which calls both functions. Anything in [] should return a
function object.

I suggest you first try to create a sample composite function object without
the whole complex machinery around and try to compile and run it first. Then
you can take the function object over into your sample.

Hope that helps,
Ovanes

On Thu, Jun 24, 2010 at 9:11 AM, Stephan Menzel wrote:
...
Ovanes,
you are right in as much as there's something wrong with what's inside
the if. Problem is, I've tried far more than just what I posted here
and I couldn't get it to compile once. So I figured I may use if_ the
wrong way.
Anyway, not posting a standalone example is generally not a good idea
but I wanted to focus more on the general idea and how to tackle it
rather than what may be wrong with a particular code example I may or
may not have. Anyway, I'll attach at least a standalone test of what I
meant here.
It shows the error nicely but contains lots of other crap I've played
around with.
Cheers,
Stephan
On Wed, Jun 23, 2010 at 6:50 PM, Ovanes Markarian
 wrote:
...
Stephan, hi!
please see my answer below.
On Wed, Jun 23, 2010 at 5:42 PM, Stephan Menzel <
stephan.menzel@gmail.com>
wrote:
...
Unless I want to add something. Unfortunately I can't always take
wrap()s output but have to modify a little. In fact, my Queue needs to
be templatized as well, modifying the behaviour of the functor. I have
a template parameter "Calling". When it is true, another function
shall be called by the functor after the method was posted. Now I
wanted to do this by phoenix:
template <bool Calling>
class Queue {
  template<typename Handler>
  void post(Handler n_handler) {
     m_iosrv.post(n_handler);
  };
...
  template
  boost::signals2::connection
connect(boost::signals2::signal<SlotSignature> &n_signal, SlotFunction
n_method) {
     return n_signal.connect(
                                 if_( CallingBack ) [
                                    post(n_method) , m_signal_callback()
                                 ] .else_ [
                                    m_iosrv.wrap( n_method )
                                 ] );
  };
...
It is difficult to conclude smth from the code without having a
self-containing example. But my assumption is that in the 'else'-branch
your
code does not generate a function object. As far as I can see in the
'if'-branch your code generates a function object using the the
comma-operator (if that operator is overloaded in Phoenix), in the
'else'-branch you just have a normal function call, which is not lazy and
does not return a function-object.
Hope that helps,
Ovanes
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