boost signal 用法与用处...

boost 的强大已经不用置疑, 仅仅的 signal 功能已经可以让无数的C++程序员们带来极大的便利. 现在, 不用再羡慕C#或java的委托和事件了, 这得归功于 boost的signal. signal的用法, 直接上代码, 代码源自于boost提供的例子:

// Document/View sample for Boost.Signals

// Copyright Keith MacDonald 2005. Use, modification and

// distribution is subject to the Boost Software License, Version

// 1.0. (See accompanying file LICENSE_1_0.txt or copy at

// http://www.boost.org/LICENSE_1_0.txt)

// For more information, see http://www.boost.org



#include <iostream>

#include <string>

#include <boost/signal.hpp>

#include <boost/bind.hpp>



class Document

{

public:

    typedef boost::signal<void (bool)>  signal_t;

    typedef boost::signals::connection  connection_t;



public:

    Document()

    {}



    connection_t connect(signal_t::slot_function_type subscriber)

    {

        return m_sig.connect(subscriber);

    }



    void disconnect(connection_t subscriber)

    {

        subscriber.disconnect();

    }



    void append(const char* s)

    {

        m_text += s;

        m_sig(true);

    }



    const std::string& getText() const

    {

        return m_text;

    }



private:

    signal_t    m_sig;

    std::string m_text;

};



class View

{

public:

    View(Document& m)

        : m_document(m)

    {

        m_connection = m_document.connect(boost::bind(&View::refresh, this, _1));

    }



    virtual ~View()

    {

        m_document.disconnect(m_connection);

    }



    virtual void refresh(bool bExtended) const = 0;



protected:

    Document&               m_document;



private:

    Document::connection_t  m_connection;

};



class TextView : public View

{

public:

    TextView(Document& doc)

        : View(doc)

    {}



    virtual void refresh(bool bExtended) const

    {

        std::cout << "TextView: " << m_document.getText() << std::endl;

    }

};



class HexView : public View

{

public:

    HexView(Document& doc)

        : View(doc)

    {}



    virtual void refresh(bool bExtended) const

    {

        const std::string&  s = m_document.getText();



        std::cout << "HexView:";



        for (std::string::const_iterator it = s.begin(); it != s.end(); ++it)

            std::cout << ' ' << std::hex << static_cast<int>(*it);



        std::cout << std::endl;

    }

};



int main(int argc, char* argv[])

{

    Document    doc;

    TextView    v1(doc);

    HexView     v2(doc);



    doc.append(argc == 2 ? argv[1] : "Hello world!");

    return 0;

}