C ++中的模板类 [英] A template class in C++

问题描述

以下C ++模板类的功能是什么？我逐行注释：

What is the function of the following C++ template class? I'm after line by line annotations:

template<class T> string toString(const T& t, bool *ok = NULL) {
         ostringstream stream;
         stream << t;
         if(ok != NULL) *ok = stream.fail() == false;
         return stream.str();
}

是否像Java的 toString c $ c>方法

Is it like Java's toString() method?

推荐答案

基本上，它将接受任何具有运算符<<定义为输出到流，并将其转换为字符串。或者，如果您传递bool varaible的地址，则会根据转换是否成功设置。

Basically, it will take any object which has an operator<< defined for output to a stream, and converts it to a string. Optionally, if you pass the address of a bool varaible, it will set that based on whether or not the conversion succeeeded.

此函数的优点是，一旦定义，一旦定义了运算符<<对于你写的一个新类，你也默默地得到一个toString（）方法。

The advantage of this function is that, once defined, as soon as you defined operator<< for a new class you write, you immedaitely also get a toString() method for it as well.

 template<class T> 
 string toString(const T& t, bool *ok = NULL) 
 { 
         ostringstream stream;     // line A
         stream << t;              // line B
         if(ok != NULL) 
               *ok = (stream.fail() == false);  // line C
         return stream.str();      // Line D
} 

• A-声明ostringstream - 输入流写入字符串


• B-使用它的运算符<
将您的对象写入流中
< ok boolean to success / failure

• D - 将流转换为标准字符串&返回。


• A - Declares an ostringstream - an output stream that writes into a string
• B - Write your object into that stream, using it's operator<<
• C - Set *ok boolean to success/failure
• D - Convert the stream into a standard string & return it.

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