Using boost.signals with boost.bind
Hi, I have one problem with boost.bind and boost.signals I can't understand. Source code is the best description, therefore #include <iostream> #include <boost/signals.hpp> #include <boost/shared_ptr.hpp> #include <boost/bind.hpp> class Func : public boost::noncopyable { public: void operator()(int i) { std::cout<<"Func::operator("<< i <<")\n"; } }; typedef boost::signal<void ()> signal_type; Func f; signal_type::slot_type binded_func = boost::bind<void>(boost::ref(f),42); int main() { boost::shared_ptr<signal_type> apSig(new signal_type()); apSig->connect(binded_func); (*apSig)(); apSig.reset(new signal_type()); boost::signals::connection con = apSig->connect(binded_func); std::cout<<"Connected: "<<con.connected()<<" Blocked: "<<con.blocked()<<"\n"; } Program output: Func::operator(42) Connected: 0 Blocked: 1 Ie, if i create new signal and then try to connect to the same slot, it fails. If I use not boost::bind object but only boost::function as slot, all works ok. I can not understand, why? I used Boost 1.34.1, gcc 4.1.2 Regards, Sergey Kishchenko
Sergey Kishchenko wrote:
I have one problem with boost.bind and boost.signals I can't understand.
I have used bind with signals in a simpler way than you have in this example. It works well for me. I don't know if you are doing it in a more complex way for a reason, but hopefully my simple version will be some help. class MyClass { public: MyClass(void) { // define the connection using bind mySignal.connect( boost::bind(&MyClass::MySlot,this,_1)); } boost::signal<void (bool)> mySignal; private: void MySlot(bool state) { // do something here to process the signal data when this is called } }; // later on, to call that signal inst = MyClass(); inst.mySignal(1); This is all pretty straightforward. This only unusual thing (for me) is the use of _1 as a marker for the first parameter. If you have a function with more parameters, then the next parameter would be _2 and so on.
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On Monday 13 October 2008 08:25 am, Sergey Kishchenko wrote:
boost::shared_ptr<signal_type> apSig(new signal_type()); apSig->connect(binded_func); (*apSig)();
apSig.reset(new signal_type()); boost::signals::connection con = apSig->connect(binded_func); std::cout<<"Connected: "<<con.connected()<<" Blocked: "<<con.blocked()<<"\n"; }
Program output:
Func::operator(42) Connected: 0 Blocked: 1
Ie, if i create new signal and then try to connect to the same slot, it fails. If I use not boost::bind object but only boost::function as slot, all works ok. I can not understand, why? I used Boost 1.34.1, gcc 4.1.2
It looks like a bug to me. In boost.signals, the slot has a shared_ptr to its signal/slot connection, which I think it uses for automatic connection management. So it looks like it was coded under the assumption a slot object (or any of its copies) would not be re-used with more than 1 signal. The slot is probably (permanently) auto-disconnecting when the first signal it was connected to is destroyed. The signals2 lib, which might get reviewed soon if there are enough reviewers, doesn't show this problem. -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.6 (GNU/Linux) iD8DBQFI9KCX5vihyNWuA4URAi7uAJ9rwpPp00P/bs03ayUHPIjW3mvtfwCgvCwn 7RqIthZ9NIY6Dc39r7fOJJk= =UTWd -----END PGP SIGNATURE-----
It works. Thank you! Signals2 lib is brilliant. I'll use it in my app. I hope this lib will be part of the next Boost release. With regards, Sergey Kishchenko 2008/10/14 Frank Mori Hess <frank.hess@nist.gov>
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1
On Monday 13 October 2008 08:25 am, Sergey Kishchenko wrote:
boost::shared_ptr<signal_type> apSig(new signal_type()); apSig->connect(binded_func); (*apSig)();
apSig.reset(new signal_type()); boost::signals::connection con = apSig->connect(binded_func); std::cout<<"Connected: "<<con.connected()<<" Blocked: "<<con.blocked()<<"\n"; }
Program output:
Func::operator(42) Connected: 0 Blocked: 1
Ie, if i create new signal and then try to connect to the same slot, it fails. If I use not boost::bind object but only boost::function as slot, all works ok. I can not understand, why? I used Boost 1.34.1, gcc 4.1.2
It looks like a bug to me. In boost.signals, the slot has a shared_ptr to its signal/slot connection, which I think it uses for automatic connection management. So it looks like it was coded under the assumption a slot object (or any of its copies) would not be re-used with more than 1 signal. The slot is probably (permanently) auto-disconnecting when the first signal it was connected to is destroyed. The signals2 lib, which might get reviewed soon if there are enough reviewers, doesn't show this problem. -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.6 (GNU/Linux)
iD8DBQFI9KCX5vihyNWuA4URAi7uAJ9rwpPp00P/bs03ayUHPIjW3mvtfwCgvCwn 7RqIthZ9NIY6Dc39r7fOJJk= =UTWd -----END PGP SIGNATURE----- _______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users
Hi Sergey, On Tue, Oct 14, 2008 at 7:27 AM, Sergey Kishchenko <voidwrk@gmail.com> wrote:
It works. Thank you! Signals2 lib is brilliant. I'll use it in my app. I hope this lib will be part of the next Boost release.
You could greatly contribute towards a possible acceptance of Signals2 by signing up to be a reviewer. You can read the original call for reviewers here: http://tinyurl.com/3jkxrg [nabble] As you have moved from using Boost.Signals to Signals2, I think your experience in transitioning would be very valuable to share during the review. Please let me know if you are interested. Kind regards, Stjepan
Hi, I had a similar problem with boost signal in version 1.36.0. I am now using Boost.Signals2 to see if fixes the issue. As it is a header only lib I copied it to existing boost 1.36.0 folder. I get the following error in VS2005 error C3861: 'TryEnterCriticalSection': identifier not found C:\Software\Boost\boost_1_36_0\boost_1_36_0\boost\signals2\detail\lwm_win32_cs.hpp 86 Are there additional libs / headers I need to add? Thanks Stjepan Rajko wrote:
Hi Sergey,
On Tue, Oct 14, 2008 at 7:27 AM, Sergey Kishchenko <voidwrk@gmail.com> wrote:
It works. Thank you! Signals2 lib is brilliant. I'll use it in my app. I hope this lib will be part of the next Boost release.
You could greatly contribute towards a possible acceptance of Signals2 by signing up to be a reviewer. You can read the original call for reviewers here: http://tinyurl.com/3jkxrg [nabble]
As you have moved from using Boost.Signals to Signals2, I think your experience in transitioning would be very valuable to share during the review. Please let me know if you are interested.
Kind regards,
Stjepan _______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users
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On Friday 17 October 2008 12:06, asio_user wrote:
I had a similar problem with boost signal in version 1.36.0. I am now using Boost.Signals2 to see if fixes the issue.
As it is a header only lib I copied it to existing boost 1.36.0 folder. I get the following error in VS2005
error C3861: 'TryEnterCriticalSection': identifier not found C:\Software\Boost\boost_1_36_0\boost_1_36_0\boost\signals2\detail\lwm_wi n32_cs.hpp 86
Are there additional libs / headers I need to add?
It seems TryEnterCriticalSection only exists if you are compiling for windows NT 4 and later. Probably the easiest thing for you to do is just delete the entire try_lock() method that uses TryEnterCriticalSection. I only added it so signals2::mutex would fully implement the Lockable concept from Boost.Thread. Signals2 doesn't actually use try_lock().
participants (6)
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asio_user -
Frank Mori Hess -
Frank Mori Hess -
Jeff Gray -
Sergey Kishchenko -
Stjepan Rajko