流异常处理

问题描述

我故意使用此方法将其写入文件，因此我尝试处理将其写入封闭文件的可能性:

Deliberately I'm having this method which writes into a file, so I tried to handle the exception of the possiblity that I'm writing into a closed file:

void printMe(ofstream& file)
{
        try
        {
            file << "\t"+m_Type+"\t"+m_Id";"+"\n";
        }
        catch (std::exception &e)
        {
            cout << "exception !! " << endl ;
        }
};

但是显然std :: exception不是关闭文件错误的适当例外，因为我故意在已关闭的文件上尝试使用此方法，但未生成我的"exception !!"注释.

But apparently std::exception is not the appropriate exception for a closed file error because I deliberately tried to use this method on an already closed file but my "exception !! " comment was not generated.

那我应该写什么例外?

推荐答案

默认情况下，流不会引发异常，但是您可以通过函数调用file.exceptions(~goodbit)告诉它们引发异常.

Streams don't throw exceptions by default, but you can tell them to throw exceptions with the function call file.exceptions(~goodbit).

相反，检测错误的常规方法只是检查流的状态:

Instead, the normal way to detect errors is simply to check the stream's state:

if (!file)
    cout << "error!! " << endl ;

这样做的原因是，在许多常见情况下，无效读取是一个小问题，而不是主要问题:

The reason for this is that there are many common situations where an invalid read is a minor issue, not a major one:

while(std::cin >> input) {
    std::cout << input << '\n';
} //read until there's no more input, or an invalid input is found
// when the read fails, that's usually not an error, we simply continue

相比:

for(;;) {
    try {
        std::cin >> input;
        std::cout << input << '\n';
    } catch(...) {
        break;
    }
}

实时观看: http://ideone.com/uWgfwj

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