爲「運營商>>」曖昧超載

Question

這是我得到的錯誤：

ambiguous overload for ‘operator>>’ in ‘contestantsInputFile >> contestantName’|

我想引用爲了傳遞一個文件的功能來讀取一個名字到一個變量稱爲contestantName。

#include <iostream> 
#include <fstream> 
#include <string> 

using namespace std; 

string contestantName = ""; 
string contestantName(ifstream &); 

int main() 
{ 
    ifstream contestantsInputFile; 
    contestantsInputFile.open("contestants_file.txt");  
    contestantName(contestantsInputFile); 
} 


string contestantName(ifstream &contestantsInputFile) 
{ 
    contestantsInputFile >> contestantName; //this is the line with the error 
    return contestantName; 
} 

Answer 1

你試圖讀取一個std :: istream的一個功能：

contestantsInputFile >> contestantName; //this is the line with the error 

這也許是更多的是你所打算（未經測試）：

#include <iostream> 
#include <fstream> 
#include <string> 

using namespace std; 

string readContestantName(ifstream &); // renamed to be a descriptive verb 

int main() 
{ 
    ifstream contestantsInputFile; 
    contestantsInputFile.open("contestants_file.txt");  
    std::string contestantName = readContestantName(contestantsInputFile); 

    std::cout << "contestant: " << contestantName << "\n"; 
} 


string readContestantName(ifstream &contestantsInputFile) 
{ 
    std::string contestantName; // new variable 
    contestantsInputFile >> contestantName; //this is the line with the error 
    return contestantName; 
}