如何更改C ++输出流以引用cout？ [英] How do I change a C++ output stream to refer to cout?

问题描述

我有一个班级，希望将其作为成员提供输出流，例如：

I have a class that I want to give an output stream as a member to, to wit:

class GameBase {
protected:
    ofstream m_OutputWriter;
...
}

该类中有一个方法需要字符串参数，然后打开m_OutputWriter指向该文件，因此可以使用标准<<<操作符；

There is a method in this class that takes a string argument and opens m_OutputWriter to point to that file, so data may be output to that file by using the standard << operator;

但是，我希望默认情况下使流指向cout，这样，如果未指定输出路径，则输出将进入控制台输出

However, what I would like is to make the stream point to cout by default, so that if the output path is not specified, output goes to the console output instead of to a file, and it will be completely transparent by the calling class, who would use

m_OutputWriter << data << endl;

将数据输出到预定的目的地。但是，我在这里尝试了其他两个示例，但它们似乎都不适合我要尝试的操作。

to output the data to the predetermined destination. Yet, I have tried a couple of the other examples here, and none of them exactly seem to fit what I'm trying to do.

我在这里缺少什么？

推荐答案

除了拥有 std :: ofstream 作为成员之外，我将使用一个返回 std :: ostream& 的函数。

In addition to having an std::ofstream as a member, I would use a function that returns an std::ostream&.

例如：

class GameBase {
    std::ofstream m_OutputWriter;
protected:
    std::ostream& getOutputWriter() {
         if (m_OutputWriter)
             return m_OutputWriter;
         else
             return std::cout;
    }
    ...
}

功能齐全示例：

#include <iostream>
#include <ostream>

std::ostream& get() {
    return std::cout;
}

int main() {
    get() << "Hello world!\n";
}

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