c++ 模板类 静态成员初始化问题

[wozhishanggao9]

template<class MessageHandlerClass>
class TimerApp
{
//friend class TimerApp;
typedef void (MessageHandlerClass::*HandlerMethod)();

public:
static void AddTimer(int interval,MessageHandlerClass *handler);

private:
static int interval_;
static HandlerMethod handler_method_; //回调函数指针
static MessageHandlerClass* handler_; //调用对象
static void OnTimer();
};


template<class MessageHandlerClass> int TimerApp<MessageHandlerClass>::interval_ = 0;
template<class MessageHandlerClass> MessageHandlerClass * TimerApp<MessageHandlerClass>::handler_ = 0;


请问handler_method_如何在类外初始化

[ChongQingJin28]

如果没有猜错的话 解决的方法应该是 “类成员指针的定义”

https://blog.csdn.net/u010126059/article/details/50768495

[kbasm]

template<class MessageHandlerClass> TimerApp<MessageHandlerClass>::HandlerMethod TimerApp<MessageHandlerClass>::handler_method_ = &TimerApp<MessageHandlerClass>::AddTimer;

[CyberLogix]

TimerApp<MessageHandlerClass>::handler_method_ = &TimerApp<MessageHandlerClass>::AddTimer;

[AlbertS]

template<class MessageHandlerClass> typename MessageHandlerClass::HandlerMethod TimerApp<MessageHandlerClass>::handler_method_ = nullptr;

感觉是这一个

[AlbertS]

最后测试了一下，应该是

template<class MessageHandlerClass> 
typename TimerApp<MessageHandlerClass>::HandlerMethod 
TimerApp<MessageHandlerClass>::handler_method_ = 0; 

完整的代码：
.h文件

class CMsgHdl
{
public:
	int m;
public:
	void handlemsg() {
		printf("handle complete!\n");
	}

};



template<class MessageHandlerClass>
class TimerApp
{
	//friend class TimerApp;
	typedef void (MessageHandlerClass::*HandlerMethod)();

public:
	static void AddTimer(int interval,MessageHandlerClass *handler){
		interval_ = interval;
		handler_ = handler;
	}
	static void AddMethod(HandlerMethod method)
	{
		handler_method_ = method;
	}
	int GetInterval() {return interval_;}

	void execute()
	{
		(handler_->*handler_method_)();
	}
	

private:
	static int interval_;
	static HandlerMethod handler_method_;    //回调函数指针
	static MessageHandlerClass* handler_;    //调用对象
	static void OnTimer();
};


template<class MessageHandlerClass> int TimerApp<MessageHandlerClass>::interval_ = 0;
template<class MessageHandlerClass> MessageHandlerClass* TimerApp<MessageHandlerClass>::handler_ = 0;

// 错误
//template<class MessageHandlerClass> TimerApp<MessageHandlerClass>::HandlerMethod TimerApp<MessageHandlerClass>::handler_method_ = &TimerApp<MessageHandlerClass>::AddTimer;

// 未调用AddMethod时编译通过,调用之后无法通过编译
//template<class MessageHandlerClass> typename MessageHandlerClass::HandlerMethod TimerApp<MessageHandlerClass>::handler_method_ = 0;

// 编译通过
template<class MessageHandlerClass> typename TimerApp<MessageHandlerClass>::HandlerMethod TimerApp<MessageHandlerClass>::handler_method_ = 0; 

.cpp文件

#include <stdio.h>
#include "templateStaticInit.h"


int main(int argc, char* argv[])
{
	TimerApp<CMsgHdl> test;
	printf("test.interval_ = %d\n", test.GetInterval());

	CMsgHdl msgHdl;

	TimerApp<CMsgHdl>::AddTimer(6, &msgHdl);
	msgHdl.handlemsg();
	
	
	TimerApp<CMsgHdl>::AddMethod(&CMsgHdl::handlemsg);

	test.execute();
	

	return 0;
}

输出
test.interval_ = 0
handle complete!
handle complete!

[sghcpt]

template<class MessageHandlerClass> typename MessageHandlerClass::HandlerMethod TimerApp<MessageHandlerClass>::handler_method_ = 0; ???????

[开心秋水]

template<class MessageHandlerClass> typename TimerApp<MessageHandlerClass>::HandlerMethod
TimerApp<MessageHandlerClass>::handler_method_ = nullptr;