c++ - 将具有绑定(bind)成员函数的 std::bind 对象传递给函数

Question

我想通过公共(public)函数将回调函数连接到 boost 信号。我可以很好地传递一个函数指针，但是如果我尝试使用 std::bind 传递一个成员函数，它将无法编译。给我错误说没有可行的转换。我应该为 App::SetCallback 函数参数使用什么类型？

#include <functional>
#include <boost/signal.hpp>
using namespace std::placeholders;  // for _1, _2, _3...

//plain simple call back function
void SimpleCallback(int value) {
//do nothing
}
//class contains a boost::signal, set callback through a public function
class App {
public:
    App() : sig_()
    {}
    typedef boost::signal<void (int value)> SigType;
    typedef std::function<void (int value)> CallbackFunType;
    //connect signal to a callback function
    void SetCallback(CallbackFunType callback) {
        sig_.connect(callback);
    }
//private: //comment this out for testing purpose.
    SigType sig_; //this is the boost::signal
};

//class that has member callback function
class MyCallback {
public:
    MyCallback():
    val(0), app()
    {}
    void MemberCb(int value){
      val = value;
    }
    void Connect() {
        auto bind_fun = std::bind(&MyCallback::MemberCb, this, _1);
        app.SetCallback(bind_fun); //this will not compile, no viable conversion
        app.sig_.connect(bind_fun); //this is fine
        app.SetCallback(SimpleCallback); //this is fine
    }
private:
    int val;
    App app;
};

int main(int argc, char **argv) {
    MyCallback my_cb;
    my_cb.Connect();
    return 1;
}

----------------更新----------------

仔细阅读 boost 信号文档，我了解到我可以传递插槽类型。这解决了我的问题

#include <functional>
#include <boost/signal.hpp>
using namespace std::placeholders;  // for _1, _2, _3...

//plain simple call back function
void SimpleCallback(int value) {
//do nothing
}
//class contains a boost::signal, set callback through a public function
class App {
public:
    App() : sig_()
    {}
    typedef boost::signal<void (int value)> SigType;
    typedef SigType::slot_type CallbackFunType;
    //typedef std::function<void (int value)> CallbackFunType;
    //connect signal to a callback function
    void SetCallback(CallbackFunType callback) {
        sig_.connect(callback);
    }
//private: //comment this out for testing purpose.
    SigType sig_; //this is the boost::signal
};

//class that has member callback function
class MyCallback {
public:
    MyCallback():
    val(0), app()
    {}
    void MemberCb(int value){
      val = value;
    }
    void Connect() {
        auto bind_fun = std::bind(&MyCallback::MemberCb, this, _1);
        app.SetCallback(bind_fun); //using SigType::slot_type
        app.sig_.connect(bind_fun);
        app.SetCallback(SimpleCallback);
    }
private:
    int val;
    App app;
};

int main(int argc, char **argv) {
    MyCallback my_cb;
    my_cb.Connect();
    return 1;
}

Answer 1

仔细阅读 boost 信号文档，我了解到我可以传递插槽类型。这解决了我的问题

#include <functional>
#include <boost/signal.hpp>
using namespace std::placeholders;  // for _1, _2, _3...

//plain simple call back function
void SimpleCallback(int value) {
//do nothing
}
//class contains a boost::signal, set callback through a public function
class App {
public:
    App() : sig_()
    {}
    typedef boost::signal<void (int value)> SigType;
    typedef SigType::slot_type CallbackFunType;
    //typedef std::function<void (int value)> CallbackFunType;
    //connect signal to a callback function
    void SetCallback(CallbackFunType callback) {
        sig_.connect(callback);
    }
//private: //comment this out for testing purpose.
    SigType sig_; //this is the boost::signal
};

//class that has member callback function
class MyCallback {
public:
    MyCallback():
    val(0), app()
    {}
    void MemberCb(int value){
      val = value;
    }
    void Connect() {
        auto bind_fun = std::bind(&MyCallback::MemberCb, this, _1);
        app.SetCallback(bind_fun); //using SigType::slot_type
        app.sig_.connect(bind_fun);
        app.SetCallback(SimpleCallback);
    }
private:
    int val;
    App app;
};

int main(int argc, char **argv) {
    MyCallback my_cb;
    my_cb.Connect();
    return 1;
}