使用getline獲取字符串對象

Question

我正在嘗試使用getline從控制台直接將用戶輸入轉換為C ++字符串對象。 但是，由於編譯器給我以下錯誤，我無法這樣做。

main.cpp: In function ‘int main(int, char**)’:
main.cpp:52:28: error: no matching function for call to ‘std::basic_ifstream<char>::getline(std::ifstream&, std::string&)’
main.cpp:52:28: note: candidates are:
/usr/include/c++/4.6/istream:599:5: note: std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::getline(std::basic_istream<_CharT, _Traits>::char_type*, std::streamsize, std::basic_istream<_CharT, _Traits>::char_type) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_istream<_CharT, _Traits>::char_type = char, std::streamsize = int]
/usr/include/c++/4.6/istream:599:5: note:   candidate expects 3 arguments, 2 provided
/usr/include/c++/4.6/istream:408:7: note: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::getline(std::basic_istream<_CharT, _Traits>::char_type*, std::streamsize) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>, std::basic_istream<_CharT, _Traits>::char_type = char, std::streamsize = int]
/usr/include/c++/4.6/istream:408:7: note:   no known conversion for argument 2 from ‘std::string {aka std::basic_string<char>}’ to ‘int’

這是源代碼：

#include <iostream>
 #include <fstream>
 #include <cmath>
 #include <cstdlib>
 #include <cstring>
 #include <string>
 #include <map>
 #include <set>
 #include <algorithm>
 #include <cstdio>

 #define MAX_LIN 1024

 using namespace std;

 typedef set<int> si;
int main(int argc, char** argv)
 {   
     string line1;
     string line2;

     map <string , si > iMap;

     if (argc != 3) { 
         fprintf(stderr,"Usage: a.out <file1> <file2>\n");
     }

     ifstream f1,f2;

     f1.open(argv[1],ifstream::in);
     f2.open(argv[2],ifstream::in);

     while(!f1.eof()) {
         getline(f1,line1);
         mParse(line1);
     }   

     while(!f2.eof()) {
         f2.getline(f2,line2);
         mParse(line2);
     }   

     f1.close();
     f2.close();


     return 0;
 }   

Answer 1

原因是：

f2.getline(f2,line2);

應該：

getline(f2,line2);

有一個std::ifstream::getline()但是它接受不同的參數。

請注意， while循環的結構不正確，因為eof()應該在讀取操作后立即檢查。 編碼循環的常用方法是：

while (getline(f2, line2))
{
    mParse(line2);
}

Answer 2

這是規范的方式：

 std::ifstream f1(argv[1]);
 std::ifstream f2(argv[2]);

 for (std::string line; std::getline(f1, line); )
 {
     mparse(line);
 }

 for (std::string line; std::getline(f2, line); )
 {
     mparse(line);
 }

請注意我們沒有寫的所有內容，每一項都應視為大寫： eof ， open ， close ， ifstream::in ， return 0 。