如何使用我的日志类像std C ++流？ [英] How to use my logging class like a std C++ stream?

问题描述

我有一个工作logger类，它输出一些文本到一个richtextbox（Win32，C ++）。问题是，我总是最终使用它像这样：

  stringstream ss; 
 ss<<一些<< someString; 
 debugLogger.log（ss.str（））; 
  

，使用它就像一个流将更加方便：

  debugLogger<<一些<< someString; 
  

有没有更好的方法转发一切到一个内部stringstream实例？

您需要实现运算符< ;< $ / code>。一般模式如下：

 模板< typename T> 
 logger& operator<<<（logger& log，T const& value）{
 log.your_stringstream<<值; 
 return log; 
} 
  

注意这是处理（非 - const ）引用，因为操作修改您的记录器。另请注意，您需要返回 log 参数才能使链接工作：

  log<< 1<< 2<< endl; 
 //与以下相同：
（（log << 1）<< 2）< endl; 
  

如果最内层操作未返回当前 log instance，所有其他操作将在编译时失败（错误的方法签名），否则将在运行时被吞下。

I've a working logger class, which outputs some text into a richtextbox (Win32, C++). Problem is, i always end up using it like this:

stringstream ss;  
ss << someInt << someString;  
debugLogger.log(ss.str());

instead, it would be much more convenient to use it like a stream as in:

debugLogger << someInt << someString;

Is there a better way than forwarding everything to an internal stringstream instance? If'd do this, when would i need to flush?

解决方案

You need to implement operator << appropriately for your class. The general pattern looks like this:

template <typename T>
logger& operator <<(logger& log, T const& value) {
    log.your_stringstream << value;
    return log;
}

Notice that this deals with (non-const) references since the operation modifies your logger. Also notice that you need to return the log parameter in order for chaining to work:

log << 1 << 2 << endl;
// is the same as:
((log << 1) << 2) << endl;

If the innermost operation didn't return the current log instance, all other operations would either fail at compile-time (wrong method signature) or would be swallowed at run-time.

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