复杂的函数调用语法

问题描述

我正在实现类似于MFC运行时类的内容.
我的目标是使用这种类似的机制在运行时创建类的实例.我已经将"CreateObject"函数存储在一个结构中，但是，我被困在调用它的语法上！

该守则的摘要如下:-

Hi,

I am implementing something similar to the MFC Runtime Class.
My aim is to create an instance of a class, at runtime, using this similar mechanism. I have stored the ''CreateObject'' function in a structure, but, I''m stuck on the syntax to call it!

The synopsis of the Code is as follows:-

class CSgObj;
typedef CSgObj*(CSgObj::*PFNCREATE)(void);


struct SG_SRVR_RTC{

	PFNCREATE pfnCreate;
};


CSgObj* CSgObj::_CreateNew(){\
	return(CSgObj*)new CSgObj;\
}

// Initialize an Instance of an SG_SRVR_RTC
static SG_SRVR_RTC classCSgObj=
	(PFNCREATE)(CSgObj::_CreateNew),
};

// Create a New object from the SG_SRVR_RTC
CSgObj* CSgObj::CreateNewObject(SG_SRVR_RTC * pRTC)
{
	ASSERT(pRTC);
	if(pRTC==NULL)return NULL;
	try{
		return this->*(pRTC->pfnCreate)();
	}
	catch(...){
		ASSERT(0);
		return NULL;
	}

}

电话:

The Call:

return this->*(pRTC->pfnCreate)();

不切芥末.我应该在那里写什么才能调用此函数.

问候，
:)
谢谢，
我知道演员不是必需的，我一步一步调试到了那里，其中包含了演员的宏.

does not cut the mustard. What should I write there to call this function.

Regards,
:)
Thanks,
I Know the cast is not required, I got there by debugging step by step,the MACRO that contains it.

return (this->*(pRTC->pfnCreate))();

绝招.问题是在哪里放置星星，箭头和条纹.
谢谢！

does the trick. The question is where to put the stars, arrows and stripes.
Thanks!

推荐答案

static SG_SRVR_RTC classCSgObj=
    (PFNCREATE)(CSgObj::_CreateNew),
};

{和&丢失，不需要强制转换.它可能很简单:

a { and an & are missing and the cast is not required. It could be as simple as:

static SG_SRVR_RTC classCSgObj=
{
    &CSgObj::_CreateNew,
};

对于通话本身，最重要的括号缺失了.应该是:

And for the call itself, most important parenthesis are missing. It should be:

return (this->*(pRTC->pfnCreate))();

或者，如果您愿意，它们的位置也很糟糕，因为以下内容似乎也可以编译:

Or if you prefer, they are badly placed as the following seems to also compile:

return (this->*pRTC->pfnCreate)();

有意义的是()具有更高的优先级，并且在整个this->*pRTC->pfnCreate表达式周围没有括号，括号将仅应用于它的直接左子表达式.也就是说，编译器将尝试先评估(pRTC->pfnCreate)()，然后评估this->* result_of_previous_expression .

实际上，它必须首先获取指向函数this->*pRTC->pfnCreate 的指针(这就是它必须放在括号中的原因)，然后在该指针上调用该函数.

It make sense are () have higher priority and without parenthesis around the whole this->*pRTC->pfnCreate expression, the parenthesis would be applied only to it immediate left sub expression. That is the compiler would try to evaluate (pRTC->pfnCreate)() first and then this->*result_of_ previous_expression.

In fact it must first get the pointer to the function this->*pRTC->pfnCreate (this is why it must be in parenthesis) and then call the function on that.

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