Ofstream沒有正確創建新文件

Question

我試過編寫一個簡單的數據庫程序。問題是，ofstream不想創建一個新文件。

下面是來自違規代碼的摘錄。

void newd() 
{ 
string name, extension, location, fname; 
cout << "Input the filename for the new database (no extension, and no backslashes)." << endl << "> "; 
getline(cin, name); 
cout << endl << "The extension (no dot). If no extension is added, the default is .cla ." << endl << "> "; 
getline(cin, extension); 
cout << endl << "The full directory (double backslashes). Enter q to quit." << endl << "Also, just fyi, this will overwrite any files that are already there." << endl << "> "; 
getline(cin, location); 
cout << endl; 
if (extension == "") 
{ 
    extension = "cla"; 
} 
if (location == "q") 
{ 
} 
else 
{ 
    fname = location + name + "." + extension; 
    cout << fname << endl; 
    ofstream writeDB(fname); 
    int n = 1; //setting a throwaway inteher 
    string tmpField, tmpEntry; //temp variable for newest field, entry 
    for(;;) 
    { 
     cout << "Input the name of the " << n << "th field. If you don't want any more, press enter." << endl; 
     getline(cin, tmpField); 
     if (tmpField == "") 
     { 
      break; 
     } 
     n++; 
     writeDB << tmpField << ": |"; 
     int j = 1; //another one 
     for (;;) 
     { 
      cout << "Enter the name of the " << j++ << "th entry for " << tmpField << "." << endl << "If you don't want any more, press enter." << endl; 
      getline(cin, tmpEntry); 
      if (tmpEntry == "") 
      { 
       break; 
      } 
      writeDB << " " << tmpEntry << " |"; 
     } 
     writeDB << "¬"; 
    } 
    cout << "Finished writing database. If you want to edit it, open it." << endl; 
} 
} 

編輯：好的，只是試圖

#include <fstream> 
using namespace std; 
int main() 
{ 
ofstream writeDB ("C:\\test.cla"); 
writeDB << "test"; 
writeDB.close(); 
return 0; 
} 

，並沒有工作，所以它是訪問權限的問題。

Answer 1

ofstream writeDB(fname); //-> replace fname with fname.c_str() 

如果您查找的ofstream的構造函數的文檔，你會看到類似這樣的： 明確的ofstream（爲const char *文件名的ios_base ::用於openmode模式=的ios_base ::出來）;

第二個參數是可選的，但第一個參數是一個const char *，而不是一個字符串。爲了解決這個問題，最簡單的方法是將你的字符串轉換爲一個叫做C字符串的字符串（char *，它基本上是一個字符數組）。要做到這一點只需使用c_str（）（它是庫的一部分）。

除此之外，您可以直接將信息放在C-str上，然後將其正常傳遞給ofstream構造函數。