istringstream不輸出正確的數據

Question

我無法讓istringstream在下面顯示的while循環中繼續。數據文件也顯示在下面。我使用輸入文件中的getline獲取第一行並將其放入istringstream lineStream中。它通過while循環一次，然後讀入第二行並返回到循環的開始處並退出而不是繼續循環。我不知道爲什麼，如果有人能幫助我，我會感激。 編輯：我有這個while循環條件的原因是因爲該文件可能包含錯誤的數據行。因此，我想確保我正在閱讀的行具有以下在數據文件中顯示的正確形式。

while(lineStream >> id >> safety){//keeps scanning in xsections until there is no more xsection IDs 

    while(lineStream >> concname){//scan in name of xsection 
     xname = xname + " " +concname; 
    } 


    getline(InputFile, inputline);//go to next xsection line 
    if(InputFile.good()){ 
     //make inputline into istringstream 
     istringstream lineStream(inputline); 
     if(lineStream.fail()){ 
      return false; 
     } 
    } 
} 

數據文件

4 0.2 speedway and mountain 
7 0.4 mountain and lee 
6 0.5 mountain and santa 

Answer 1

在所提出的代碼，＆hellip;

while(lineStream >> id >> safety){//keeps scanning in xsections until there is no more xsection IDs 

    while(lineStream >> concname){//scan in name of xsection 
     xname = xname + " " +concname; 
    } 

    getline(InputFile, inputline);//go to next xsection line 
    if(InputFile.good()){ 
     //make inputline into istringstream 
     istringstream lineStream(inputline); 
     if(lineStream.fail()){ 
      return false; 
     } 
    } 
} 

＆hellip; lineStream的內部聲明聲明瞭一個局部對象，當執行超出該塊時該局部對象不再存在，並且不影響外循環中使用的流。

---

一個可能的解決辦法是反轉代碼一點點，像這樣：

while(getline(InputFile, inputline)) 
{ 
    istringstream lineStream(inputline); 

    if(lineStream >> id >> safety) 
    { 
     while(lineStream >> concname) 
     { 
      xname = xname + " " +concname; 
     } 
     // Do something with the collected info for this line 
    } 
}