如何QDebug（）<<东东;自动添加换行符？ [英] How does QDebug() << stuff; add a newline automatically?

问题描述

我试图实现我自己的QDebug（）样式调试输出流，这基本上是我到目前为止：

I'm trying to implement my own QDebug() style debug-output stream, this is basically what I have so far:

struct debug
{
#if defined(DEBUG)
    template<typename T>
    std::ostream& operator<<(T const& a) const
    {
        std::cout << a;
        return std::cout;
    }
#else
    template<typename T>
    debug const& operator<<(T const&) const
    {
        return *this;
    }

    /* must handle manipulators (endl) separately:
     * manipulators are functions that take a stream& as argument and return a
     * stream&
     */
    debug const& operator<<(std::ostream& (*manip)(std::ostream&)) const
    {
        // do nothing with the manipulator
        return *this;
    }
#endif
};

典型用法：

debug() << "stuff" << "more stuff" << std::endl;

但我不想添加std :: endl;

But I'd like not to have to add std::endl;

我的问题基本上是，我如何告诉何时返回类型的操作符<将不被另一个运营商使用< （所以追加endl）？

My question is basically, how can I tell when the return type of operator<< isn't going to be used by another operator<< (and so append endl)?

我可以想到的唯一的方法是实现这样的东西是创建一个列表，打印每个临时对象由debug（）创建，然后在〜debug（）中打印所有内容，以及尾随的换行符（我可以做聪明的事情，如插入空格），但显然这不是理想的，因为我不保证临时对象将被销毁，直到作用域结束（或者我？）。

The only way I can think of to achieve anything like this would be to create a list of things to print with associated with each temporary object created by debug(), then to print everything, along with trailing newline (and I could do clever things like inserting spaces) in ~debug(), but obviously this is not ideal since I don't have a guarantee that the temporary object is going to be destroyed until the end of the scope (or do I?).

推荐答案

Qt使用类似@ Evan。请参见 qdebug.h的版本作为实现细节，但是它们将所有内容都转换为基础文本流，然后在销毁qDebug（）返回的临时QDebug对象时刷新流和结束行。

Qt uses a method similar to @Evan. See a version of qdebug.h for the implementation details, but they stream everything to an underlying text stream, and then flush the stream and an end-line on destruction of the temporary QDebug object returned by qDebug().

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