C++ Boost signals and slots connection - c++

Question

I am trying to connect a gui to my logic thread using boosts signals and slots, the logic class has a neat method to connect functions to the signal.
Here is a simplified replica of the locig class:
#include <boost/signals2.hpp>
#include <boost/function.hpp>
typedef boost::signals2::signal<void (const double&)> some_signal;
typedef some_signal::slot_type some_slot;
class LogicClass {
some_signal sig;
public:
LogicClass();
~LogicClass();
void register_callback(boost::function<void (const double&)>) {
sig.connect(boost::bind(&LogicClass::doStuff(), this, _1));
}
void doStuff(); // Does a bunch of stuff in a separate thread and fires LogicClass::sig every now and then
}
Here is a simplified replica of the gui class
#include <boost/signals2.hpp>
#include <QWidget.h>
class GuiClass : public QWidget {
Q_OBJECT //etc. etc. w.r.t. Qt stuff
public:
GuiClass ();
~GuiClass ();
void draw_stuff(const double&); // Want this to listen to LogicClass::sig;
}
At some point in my code the gui class is already instantiated but the logic class isn't. So i want to instantiate the LogicClass and subscribe the GuiClass::draw_stuff(const double&) to the LogicClass::sig signal. Something like
#include <logicclass.h>
#include <guiclass.h>
GuiClass *gui; //Was initialized elsewhere, but available here;
void some_function() {
LogicClass *logic = new LogicClass();
logic->register_callback(gui->drawStuff);
logic->do_stuff(); //Start drawing on the gui
delete logic;
}
This unfortunately doesn't work. Goes without saying it would like it to work very much!
I know Qt also implements signals & slots, but i would like to use boost for portability with other UI libraries.

Answer 1

Looks like you meant to bind draw_stuff instead of hardcoded doStuff inside of that register function:
logic->register_callback(boost::bind(&GuiClass::draw_stuff, gui, _1));
And then
void register_callback(boost::function<void(double)> handler) {
sig.connect(handler);
}
Simple Demo
Live On Coliru
#include <boost/bind.hpp>
#include <boost/function.hpp>
#include <boost/signals2.hpp>
#include <boost/thread.hpp>
#include <iostream>
typedef boost::signals2::signal<void(double)> some_signal;
typedef some_signal::slot_type some_slot;
class LogicClass {
some_signal sig;
public:
LogicClass() = default;
~LogicClass() = default;
void register_callback(boost::function<void(double)> handler) {
sig.connect(handler);
}
void doStuff() {
std::cout << __PRETTY_FUNCTION__ << "\n";
// Does a bunch of stuff in a separate thread and fires LogicClass::sig every now and then
boost::thread([this] {
for (double d : {1,2,3}) {
boost::this_thread::sleep_for(boost::chrono::milliseconds(500));
sig(d);
}
}).join();
}
};
#define Q_OBJECT
struct QWidget {};
class GuiClass : public QWidget {
Q_OBJECT // etc. etc. w.r.t. Qt stuff
public:
GuiClass() = default;
~GuiClass() = default;
void draw_stuff(double v) { std::cout << __PRETTY_FUNCTION__ << "(" << v << ")\n"; }
};
//#include <logicclass.h>
//#include <guiclass.h>
GuiClass *gui; // Was initialized elsewhere, but available here;
void some_function() {
LogicClass *logic = new LogicClass();
logic->register_callback(boost::bind(&GuiClass::draw_stuff, gui, _1));
logic->doStuff(); // Start drawing on the gui
delete logic;
}
int main() {
GuiClass gui_instance;
gui = &gui_instance;
some_function();
}
Prints
void LogicClass::doStuff()
void GuiClass::draw_stuff(double)(1)
void GuiClass::draw_stuff(double)(2)
void GuiClass::draw_stuff(double)(3)