如何在C++中重寫++運算符，然後使用覆蓋<<運算符打印輸出？

Question

我想學習C++重寫操作符。但我堅持這一點：

..\src\application.cpp: In function `int main()':

..\src\application.cpp:29: error: no match for 'operator<<' in 'std::operator<< [with _Traits = std::char_traits](((std::basic_ostream >&)(&std::cout)), ((const char*)"Poly A: ")) << (&A)->Poly::operator++(0)'

下面是導致錯誤的路線，看來，我的後置操作不返回任何東西打印：我有一個Poly.h和

cout << "Poly A: " << A++ << endl; 

Poly.cpp文件：

class Poly{ 
friend istream& operator>>(istream &in, Poly &robject); 
friend ostream& operator<<(ostream &out, Poly &robject); 
public: 
    Poly(); 

    Poly operator++(int); 
    Poly operator++();  
private: 
    int data[2]; 
}; 

Poly.cpp：

Poly Poly::operator++(){ 
data[0]+=1; 
data[1]+=1; 
return *this;} 

Poly Poly::operator++ (int){ 
    Poly result(data[0], data[1]); 
     ++(*this); 
    return result; 
} 
ostream& operator<<(ostream &out, Poly &robject){ 
out << "(" << robject.data[0] << ", " << robject.data[1] << ")"; 
return out; 
} 

Answer 1

我認爲問題是，你宣佈你的參數作爲參考：

ostream& operator<<(ostream &out, Poly &robject) 

參考不會綁定到您從operator++返回臨時工。 如果你使Poly參數爲const參考，你應該可以輸出它。