如何從整個代碼的函數中打開一個文件？

Question

我正在研究一個簡單的C++腳本，並希望在一個函數中打開一個文件的整個過程。但是，當我嘗試時，我的主要功能中出現錯誤。誰能幫我？這是我的代碼：

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

using namespace std; 

string openFile(string fileName); 
int main(void) 
{ 
    string fileName; 
    cout << "Please input the file name (including the extension) for this code to read from." << endl; 
    cin >> fileName; 

    openFile(fileName); 

    fout << "File has been opened" << endl; 
    return 0; 
} 

string openFile(string fileName) 
{ 
    ifstream fin(fileName); 
    if (fin.good()) 
    { 
     ofstream fout("Output"); 
     cout << fixed << setprecision(1); 
     fout << fixed << setprecision(1); 
     //Set the output to console and file to be to two decimal places and 
     //not in scientific notation 
    } 
    else 
    { 
     exit(0); 
    } 
} 

Answer 1

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

    using namespace std; 

    ofstream fout; 
    string openFile(string fileName); 
    void closeFile(); 

    int main(void) 
    { 
     string fileName; 
     cout << "Please input the file name (including the extension) for this code to read from." << endl; 
     cin >> fileName; 

     openFile(fileName); 
     if (fout.good()) //use fout in any way in this file by cheking .good() 
      cout << "File has been opened" << endl; 
     closeFile(); 
     return 0; 
    } 

    string openFile(string fileName) 
    { 
     cout << fixed << setprecision(1); 
     fout.open(fileName.c_str()); 
     if (fout.good()) { 
      fout << fixed << setprecision(1); 
      cout<<"Output file opened"; 
     } 
    } 
    void closeFile() 
    { 
     fout.close(); 
    } 

Answer 2

你的代碼有很多很多的缺陷，

1. fout << "File has been opened" << endl;，應該是，

   cout << "File has been opened" << endl;

2. 不能再redifine相同varible。

   ofstream fout("Output");// first 
   cout << fixed << setprecision(1); 
   fout << fixed << setprecision(1); 
   //Set the output to console and file to be to two decimal places and 
   //not in scientific notation 
   ofstream fout("Tax Output.txt");//second 
   

在最後一行給一些其他的名字變量。

你傳入std::string，在這裏應該通過const char *，

ifstream fin(fileName);

應該是，

ifstream fin(fileName.c_str());