C ++反復出現的模板模式，語法錯誤

Question

我試圖編寫一個模板事件類，並在此基類中保留盡可能多的代碼。 我正在使用反復出現的模板模式，但是我不確定我在這里做什么。

template< class EventType >
class Event
{
protected:

    std::vector< EventType::Listener * > m_aListeners;

public:

    void operator += ( EventType::Listener * pListener )
    {
        m_aListeners.push_back( pListener );
    }

    void operator -= ( EventType::Listener * pListener )
    {
        std::vector< EventType::Listener * >::reverse_iterator revIter = m_aListeners.rbegin();
        for( ; revIter != m_aListeners.rend(); ++revIter )
            if( revIter == pListener )
            {
                m_aListeners.remove( revIter );
                break;
            }
    }

    void Trigger( EventType::Data * pData )
    {
        std::vector< EventType::Listener * >::iterator iter = m_aListeners.begin();
        for( ; iter != m_aListeners.end(); ++iter )
            CallListenert( iter, pData );
    }

    virtual void CallListener( EventType::Listener * pListener, EventType::Data * pData ) = 0;
};

以及給定事件類型的子類：

class ConnectionSuccessEvent : public Event< ConnectionSuccessEvent >
{
public:

    class Data
    {
    public:
        Data( int iVal ) : m_iVal( iVal ) { }
    public:
        const int m_iVal;
    };

    class Listener
    {
    public:
        virtual ~Listener() { }
        virtual void OnConnectionSuccess( Data * pEventData ) = 0;
    };

    void CallListener( Listener * pListener, Data * pData )
    {
        pListener->OnConnectionSuccess( pData );
    }
};

還有一個實現監聽器類的類：

class MyClass :  public ConnectionSuccessEvent::Listener
{
public:

    void OnConnectionSuccess( ConnectionSuccessEvent::Data * pEventData )
    {
        std::cout << "OnConnectionSuccess : " << pEventData->m_iVal << std::endl;
    }
};

我使用如下：

MyClass oMyClassInstance;

ConnectionSuccessEvent oOnConnectionSuccess;

oOnConnectionSuccess += & oMyClassInstance;
oOnConnectionSuccess += & oMyClassInstance;

ConnectionSuccessEvent::Data oData( 456 );
oOnConnectionSuccess.Trigger( & oData );

oOnConnectionSuccess -= & oMyClassInstance;
oOnConnectionSuccess -= & oMyClassInstance;

這導致了幾個編譯錯誤，第一個是：

錯誤2錯誤C2059：語法錯誤：'>'c：\\ dev \\ eventtest \\ event.h 16

對應於向量m_aListeners的聲明。

我有兩個問題：

• 是什么導致我的錯誤？ 我不能在類Event中使用EventType :: Listener嗎？

• 奇怪的重復模式怎么可能？ 我的意思是，要定義，派生類需要定義其父類。 但是因為它是父類，所以它的父類需要定義其模板參數類（即它的基類），所以這是一個問題，因為要定義一個，首先需要定義另一個。 這就像在類B中有一個實例A，在類A中有一個實例obB。

謝謝 ！

編輯：我不能使用C ++ 11。

Answer 1

我找到了一個可以接受的丑陋方法！

包含事件對象行為的基本事件類。

template< class EventListenerType, class EventDataType >
class BaseEvent
{
private:

    std::vector< EventListenerType * > m_aListeners;

public:

    void operator += ( EventListenerType * pListener )
    {
        m_aListeners.push_back( pListener );
    }

    void operator -= ( EventListenerType * pListener )
    {
        // When nI is 0 and gets decremented (i.e would be < 0), it "underflows" and
        // becomes >= m_aListeners.size(), so we can detect that the last element (i.e 
        // the first in position ) has been treated when nI >= m_aListeners.size().

        for( size_t nI = m_aListeners.size() - 1; nI <= m_aListeners.size(); --nI )
        {
            if( m_aListeners[ nI ] == pListener )
            {
                m_aListeners.erase( m_aListeners.begin() + nI );
                break;
            }
        }
    }

    void Trigger( EventDataType * pData )
    {
        for( size_t nI = 0; nI < m_aListeners.size(); ++nI )
            m_aListeners[ nI ]->OnEvent( pData );
    }
};

和：

template< class EventDataType >
class EventListener
{
public:

    virtual ~EventListener() { }

    virtual void OnEvent( const EventDataType * pData ) = 0;
};

ConnectionSuccessEvent特定的東西：

class ConnectionSuccessEventData
{
public:
    const int m_iVal;
    ConnectionSuccessEventData( int iVal ) : m_iVal( iVal ) { }
};

typedef EventListener< ConnectionSuccessEventData > ConnectionSuccessEventListener;
typedef BaseEvent< ConnectionSuccessEventListener, ConnectionSuccessEventData > ConnectionSuccessEvent;

DataReceivedEvent特定內容：

class DataReceivedEventData
{
public:
    const float m_fVal;
    DataReceivedEventData( float fVal ) : m_fVal( fVal ) { }
};

typedef EventListener< DataReceivedEventData > DataReceivedEventListener;
typedef BaseEvent< DataReceivedEventListener, DataReceivedEventData > DataReceivedEvent;

偵聽器類：

class MyClass : public ConnectionSuccessEventListener, public DataReceivedEventListener
{
public:

    void OnEvent( const ConnectionSuccessEventData * pData )
    {
        std::cout << "Connection success event : " << pData->m_iVal << std::endl;
    }

    void OnEvent( const DataReceivedEventData * pData )
    {
        std::cout << "Data received event : " << pData->m_fVal << std::endl;
    }
};

用法：

MyClass oMyClassInstance;

ConnectionSuccessEvent oOnConnectionSuccess;
DataReceivedEvent oOnDataReceived;

oOnConnectionSuccess += & oMyClassInstance;
oOnDataReceived += & oMyClassInstance;
oOnConnectionSuccess += & oMyClassInstance;
oOnDataReceived += & oMyClassInstance;

ConnectionSuccessEventData oConnectionSuccessData( 123 );
oOnConnectionSuccess.Trigger( & oConnectionSuccessData );

DataReceivedEventData oDataReceivedData( 0.0f );
oOnDataReceived.Trigger( & oDataReceivedData );

oOnDataReceived += & oMyClassInstance;
oOnConnectionSuccess -= & oMyClassInstance;
oOnDataReceived += & oMyClassInstance;
oOnConnectionSuccess -= & oMyClassInstance;