Cin has no operand >> | 易学教程

问题

I don't understand why this isn't working. For some reason I'm getting the error:

error C2678: binary '>>' : no operator found which takes a left-hand operand of type 'std::istream' (or there is no acceptable conversion)

I'm doing this in Visual Studio2010 C++ Express if that helps. Not sure why its handing me this error I've done other programs using cin...

My Code:

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

int main(int argc, char* argv){
    string file;

    if (argc > 1)
    {
        file = argv[1];
    }
    else
    {
        cout << "Please Enter Your Filename: ";
        cin >> file;
    }
}

回答1:

include <string>

On top of that I suggest you use getline instead as >> will stop at the first word in your input.

Example:

std::cin >> file; // User inputs C:\Users\Andrew Finnell\Documents\MyFile.txt

The result is "C:\Users\Andrew", quite unexpected considering that the data is not consumed until the newline and, the next std::string read will automatically be consumed and filled with "Finnell\Documnts\MyFile.txt"

std::getline(std::cin, file);

This will consume all text until the newline.

回答2:

You forgot to include <string>, which is where that function is defined. Remember that each type defines its own operator>> as a static function for manipulation via a stream. an input stream could not possibly be written to account for all types that may be created in the future, so it is extended this way.

来源：https://stackoverflow.com/questions/10183008/cin-has-no-operand

标签

c++

iostream

cin