使varargs异常构造函数填充stringstream [英] Make varargs Exception constructor to fill stringstream

问题描述

基本上我正在做Exception类，我想要能够很容易地传递调试细节，例如：

Basically I am making Exception class and I want to be able to pass debug details easily, such as this:

var error = someFunction();
if(error!=0) {
    throw MyException("someFunction ended with error state #",error,'.');
}

这将需要 MyException 类接受可以由 stringstream 处理的varargs参数。我不知道我该怎么做，我想象是这样：

This would require the MyException class to accept varargs arguments that can be processed by stringstream. I have no idea how exactly could I do that, what I imagine is this:

#include <string>
#include <sstream>
template /* MUCH DEEP MAGIC HERE**/
MyException::MyException(/* MOAR DEEP MAGIC!!! **/) {
    std::stringstream ss;
    for(/** ITERATE THROUGH MORE MAGIC**/) {
        ss<</**FETCH MAGIC STUFF**/;
    }
    this->message = ss.str();
}

推荐答案

当扩展参数包这样做。这里是魔法。

You can abuse the comma operator when expanding the parameter pack to do this. Here be that magic.

template<typename Stream, typename ...Args>
Stream& print(Stream& o, const Args&... args)
{
    auto x = { ((o << args), 0)... };
    return o;
}

这会将所有参数一次发送到一个流，逗号后面的表达式构造整数的初始化列表。

This sends all arguments to the stream one at a time while taking the result of the expression after the comma constructing an initializer list of integers.

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