[英]C++ Curiously recurring template pattern, syntax error
我试图编写一个模板事件类,并在此基类中保留尽可能多的代码。 我正在使用反复出现的模板模式,但是我不确定我在这里做什么。
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;
};
以及给定事件类型的子类:
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 );
}
};
还有一个实现监听器类的类:
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;
这导致了几个编译错误,第一个是:
错误2错误C2059:语法错误:'>'c:\\ dev \\ eventtest \\ event.h 16
对应于向量m_aListeners的声明。
我有两个问题:
是什么导致我的错误? 我不能在类Event中使用EventType :: Listener吗?
奇怪的重复模式怎么可能? 我的意思是,要定义,派生类需要定义其父类。 但是因为它是父类,所以它的父类需要定义其模板参数类(即它的基类),所以这是一个问题,因为要定义一个,首先需要定义另一个。 这就像在类B中有一个实例A,在类A中有一个实例obB。
谢谢 !
编辑:我不能使用C ++ 11。
我找到了一个可以接受的丑陋方法!
包含事件对象行为的基本事件类。
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特定的东西:
class ConnectionSuccessEventData
{
public:
const int m_iVal;
ConnectionSuccessEventData( int iVal ) : m_iVal( iVal ) { }
};
typedef EventListener< ConnectionSuccessEventData > ConnectionSuccessEventListener;
typedef BaseEvent< ConnectionSuccessEventListener, ConnectionSuccessEventData > ConnectionSuccessEvent;
DataReceivedEvent特定内容:
class DataReceivedEventData
{
public:
const float m_fVal;
DataReceivedEventData( float fVal ) : m_fVal( fVal ) { }
};
typedef EventListener< DataReceivedEventData > DataReceivedEventListener;
typedef BaseEvent< DataReceivedEventListener, DataReceivedEventData > DataReceivedEvent;
侦听器类:
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;
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.