使用运算符将​​字符串流传递给istream >>

Question

我试图将字符串流传递到具有>>声明和定义的重载提取运算符的对象（类）中。例如，object1中重载提取运算符的声明为

friend istream& operator >>(istream& in, Object1& input);

在object2中，我的声明几乎相同

friend istream& operator >>(istream& in, Object2& input);

在object1提取功能期间，函数。获取一行，将其转换为字符串流，并尝试使用Object2的extract（>>）运算符。

istream& operator >>(istream& in, Object1& input){
     Object2 secondObj;
     string data;
     string token;
     in>>data;
     in.ignore();
     token = GetToken(data, ' ', someint); //This is designed to take a part of data
     stringstream ss(token); // I copied token into ss
     ss >> secondObj; // This is where I run into problems.
}

我得到了错误No match for operator >>。这是因为我需要将stringstream转换为istream吗？如果是这样，我该怎么做？

最小程序如下所示：在main.cpp中：

#include "Object1.h"
#include "Object2.h"
#include "dataClass.h"
using namespace std;
int main(){
    Object1<dataClass> firstObj;
    cin>>firstObj;
    cout<<firstObj<<endl;
}

在Object1.h中：

#ifdef OBJECT1_H_
#define OBJECT1_H_
#include <iostream>
#include <string>
#include <cstddef>
#include "Object2.h"
template<class T>
class Object1{
public:
    //Assume I made the Big 3
    template<class U>friend istream& operator >>(istream& in, Object1<U>& input);
    template<class U>friend ostream& operator <<(ostream& out, const Object1<U>& output);
private:
    Object2<T>* head;
};
template<class T>
istream& operator >>(istream& in, Object1<T>& input){
     Object2 secondObj;
     string data;
     string token;
     in>>data;
     in.ignore();
     token = GetToken(data, ' ', someint); //This is designed to take a part of data
     stringstream ss(token); // I copied token into ss
     ss >> secondObj; // This is where I run into problems.
}
template<class T>
ostream& operator <<(ostream out, const Object1<T>& output){
     Object2<T>* ptr;
     while(GetNextPtr(ptr) != NULL){
         cout<<ptr;
         ptr = GetNextPtr(ptr); //Assume that I have this function in Object2.h
     }
}

Object2.h文件看起来与Object1.h类似，除了：

template<class T>
class Object2{
public:
//similar istream and ostream funcions of Object1
//a GetNextPtr function
private:
    T data;
    Object2<T>* next;
};
template<class T>
istream& operator >>(istream& in, Object2<T>& input){
      in>>data; //data is the private member variable in Object2.
                //it is of a templated class type.
}

Answer 1

以下编译良好：

#include <string>
#include <sstream>
#include <iostream>

using namespace std;

struct X{};

struct Y{};

istream& operator>>(istream&, X&) {}

istream& operator>>(istream&, Y&)
{
    stringstream ss("foo");

    X x;
    ss >> x;
}

int main()
{
    Y y;
    cin >> y;
}

你的问题一定在其他地方

您可以发布一个完整的最小独立程序来演示该问题吗？或者只是你的函数的声明和定义istream& operator >>(istream& in, Object2& input)？它是否在翻译单元中的 Object1 版本之前声明？