重载<<运算符std :: ostream [英] Overloading << operator for std::ostream

问题描述

  ostream& operator<<<（ostream& osObject，const storageRentals& rentals）
 {
 osObject< rental.summaryReport（）; 
 return osObject; 
} 
  

summaryReport（）是一个void函数，它给我一个错误：

无操作符<匹配这些操作数

但错误不存在，如果我更改 summaryReport 函数到一个 int ，但我的问题是，你必须返回一个值，它是在屏幕上打印出来。

  void storageRentals :: summaryReport（）const 
 {
 for（int count = 0; count< 8; count ++）
 cout<< 单位：< count + 1< < stoUnits [count]< endl; 
} 
  

有任何方法来重载 cout< ; c>你应该定义 summartReport code>以 ostream& 作为参数，如下所示：

  std :: ostream& storageRentals :: summaryReport（std :: ostream& out）const 
 {
 //使用out而不是cout 
 for（int count = 0; count< 8; count ++）
 out<< 单位：< count + 1< < stoUnits [count]< endl; 
 
 return out; // return so that op<<可以只是一条线！ 
} 
  

然后调用：

  ostream& operator<<<（ostream& osObject，const storageRentals& rentals）
 {
 return rentals.summaryReport（osObject）; //只有一行！ 
} 
  

顺便说一句，它不是调用overloading cout。您应该说， std :: ostream 重载运算符<< / p>


ostream& operator <<(ostream& osObject, const storageRentals& rentals)
{
    osObject << rentals.summaryReport();
    return osObject;
}

summaryReport() is a void function, and it is giving me an error:

no operator "<<" matches these operands

but the error is not there if I change the summaryReport function to an int, but the problem I have with that is you have to return a value, and it is printing it out on the screen.

void storageRentals::summaryReport() const
{
   for (int count = 0; count < 8; count++)
      cout << "Unit: " << count + 1 << "    " << stoUnits[count] << endl;
}

Is there any way to overload cout << with a void function?

解决方案

You should define summartReport taking ostream& as parameter, as shown here:

std::ostream&  storageRentals::summaryReport(std::ostream & out) const
{
    //use out instead of cout
    for (int count = 0; count < 8; count++)
        out << "Unit: " << count + 1 << "    " << stoUnits[count] << endl;

    return out; //return so that op<< can be just one line!
}

then call it as:

ostream& operator <<(ostream& osObject, const storageRentals& rentals)
{
    return rentals.summaryReport(osObject); //just one line!
}

By the way, it is not called "overloading cout". You should say, "overloading operator<< for std::ostream.

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