帶字符的流問題

Question

我有一個成員函數，要求用戶輸入文件名，然後從文件輸入並在不同的函數上使用它。每個函數都帶有字符或字符。然而它並不完全執行這些功能。我認爲它與從文件中挑選數據然後使它們變成字符有關？是否有可能使用sstream從文件中分離元素，然後將這些元素用作字符？

void My_Function::file() 
{ 
    fstream data;//file input 
    char filename[80]; 
    string line; 
    int first; 
    char sec, third, fourth; 

    cout<<"Enter file name: \n"; 
    cin>>fileName; 
    data.open(fileName); 

    while(getline(data,line)) 
    { 
     stringstream str(line); 
     istringstream ins; 
     ins.str(line);//get line 
     str >> first >> sec >> third >> fourth; 

     switch(first) 
     { 
      case 1: 
        add(sec); 
        break; 
      case 2: 
        delete_item(sec, third); 
        break; 
      case 3: 
        print_everything(sec, third); 
        break; 
      case 4: 
        makenew(sec, third); 
        break; 
      case 5: 
        find(sec, third, fourth); 
        break; 
      case 0: 
        break; 
     } 
    } 
} 

Answer 1

書面您的代碼無法編譯，但固定「文件名」 /「文件名」的問題後，在我看來，這個特殊的部分做的事情是應該做的。你應該考慮嘗試澄清你的問題，並解釋你期望的代碼做什麼以及它與實際做法有什麼不同。 「不完全執行這些功能」的含義確實有點不明確！

爲了測試這樣的事情，它有時是有益的像

delete_item(sec, third); 

線改爲

cout << "delete_item(" << sec << ", " << third << ")\n"; 

Answer 2

您可能需要更改

stringstream str(line); 
istringstream ins; 
ins.str(line);//get line 
str >> first >> sec >> third >> fourth; 

到

istringstream ins(line); 
ins >> first >> sec >> third >> fourth; 

Answer 3

我認爲你的問題是與數據。對於你的代碼工作，它應該是如下形式：

0 1 2 3 
1 1 2 3 
2 1 2 3 
3 1 2 3 
4 1 2 3 
5 1 2 3 

發佈您的數據樣本，供我們檢查。

此代碼按預期工作與數據（你的代碼在主與COUTS）：

#include <iostream> 
#include <sstream> 
#include <fstream> 
using namespace std; 

int main() 
{ 
    fstream data;//file input 
    char fileName[80]; 
    string line; 
    int first; 
    char sec, third, fourth; 

    cout<<"Enter file name: \n"; 
    cin>>fileName; 
    data.open(fileName); 

    while(getline(data,line)) 
    { 
     stringstream str(line); 
     istringstream ins; 
     ins.str(line);//get line 
     str >> first >> sec >> third >> fourth; 

     cout << "line = " << str.str() << endl; 

     switch(first) 
     { 
      case 1: 
        cout << "add(sec); " << sec << endl; 
        break; 
      case 2: 
        cout << "delete_item(sec, third); " << sec << ", " << third << endl; 
        break; 
      case 3: 
        cout << "print_everything(sec, third); " << sec << ", " << third << endl; 
        break; 
      case 4: 
        cout << "makenew(sec, third);" << sec << ", " << third << endl; 
        break; 
      case 5: 
        cout << "find(sec, third, fourth); " << sec << ", " << third << ", " << fourth << endl; 
        break; 
      case 0: 
        cout << "0" << endl; 
        break; 
     } 
    } 
} 

與輸出：

Enter file name: 
toto 
line = 0 1 2 3 
0 
line = 1 1 2 3 
add(sec); 1 
line = 2 1 2 3 
delete_item(sec, third); 1, 2 
line = 3 1 2 3 
print_everything(sec, third); 1, 2 
line = 4 1 2 3 
makenew(sec, third);1, 2 
line = 5 1 2 3 
find(sec, third, fourth); 1, 2, 3 
line = 
find(sec, third, fourth); 1, 2, 3