c++ - 标准没有成员'getline'？

Question

我正在尝试使用 std::getline，但我的编译器告诉我 getline 没有被识别？

#include <iostream>
#include <cstdio>
#include <cmath>
#include <cstring>
#include <fstream>
#include <cstdlib>

int main(){
    using namespace std;
    string line;
    ifstream ifile("test.in");
    if(ifile.is_open()){
        while(ifile.good()){
            getline(ifile,line);
        }
    }
}

Answer 1

std::getline is defined in the string header.

#include <string>

Also, your code isn't using anything from cstring, cstdio, cmath, or cstdlib; why bother including these?

EDIT: To clarify the confusion regarding the cstring and string headers, cstring pulls the contents of the C runtime library's string.h into the std namespace; string is part of the C++ standard library and contains getline, std::basic_string<> (and its specializations std::string and std::wstring), etc. -- two very different headers.

Answer 2

正如 ildjarn 指出的那样，该函数是在中声明的<string>，我很惊讶您在以下位置没有收到错误：

string line;

另外，这个：

 while(ifile.good()){
      getline(ifile,line);
 }

不是编写读取循环的方法。您必须测试读取操作是否成功，而不是当前流状态。你要：

while( getline(ifile,line) ) {
}

Answer 3

发生这种情况是因为 getline 来自字符串库，您需要#include <string>或#include <cstring>