Re: [Boost-users] [Signals] trackable detection for user defined callabcks

Subject: Re: [Boost-users] [Signals] trackable detection for user defined callabcks
From: Igor R (boost.lists_at_[hidden])
Date: 2011-10-28 12:09:43

>> Hehe it is:
>> http://www.boost.org/doc/libs/1_47_0/doc/html/boost/signals/trackable.html
>
> Ah, so I should provide appropriate visit_each() overload for my callback type?
> Can't say I understand what it is suppose to do tho. Example for Boost.Function
> would be great ;)

Sorry, I probably misunderstood you. I also don't quite understand
what the documentation means by saying "User-defined function
objects<...>do not implement the required interfaces
for trackable object detection". Any user-defined object can inherit
from signals::trackable and thus "implement the required interfaces".
boost::function (and of course, std::function etc) really doesn't
provide such a functionality as far as I know, and I'm not sure it's
possible to add it externally.

> Signals2 requires objects to be managed by shared_ptr which imho is more
intrusive (in a sense of class design enforcement) than original Signals. My
objects are kept in ptr_ and intrusive containers and it is trivial to make
them trackable but impossible to make them being managed by shared_ptr.

If your objects have to be managed by other types of smart-ptrs, you
still can use weak_ptr for tracking:
struct your_class
{
  your_class() : track_(new int())
  {}
private:
  shared_ptr<void> track_;
}

...now pass track_ for any tracking purposes.
If you've got a single-threaded design it seems to be safe, doesn't it.

> Additionally, within specific sub-systems signal-slot connections are single-threaded and using:
> namespace bs2 = boost::signals2;
> using bs2::keywords;
> bs2::signal_type<void (int), mutex_type<bs2::dummy_mutex> >::type sig;
> instead of:
> signal<void(int)> sig;
> especially multiple times in single class definition is just horrible. Or am I missing some easy way to redefine default mutex?

Well... at least, you can typedef mutex_type<bs2::dummy_mutex> :).