How do I fix a “No instance of overloaded function” error with cin.getline?

问题

string add_text()
{
    const int string_size(30);
    string add_string;
    cin.getline (add_string,string_size,'\n');
    return add_string;
}

When I compile the program with the function above, I get an error. Note that I am using using namespace std; earlier in the program. If it helps I am using Code Blocks and have also tried compiling the program using the Visual Studio 11 Professional Beta.

The Error:

C:\Users\Jonathan\Documents\Code_Blocks\test_12\main.cpp|32|error: no matching function for call to 'std::basic_istream<char, std::char_traits<char> ::getline(std::string&, const int&, char)'|

Any help with this issue will be greatly appreciated, thanks in advance!

回答1:

You're calling std::istream::getline(char *, streamsize) - you can see it requires a char * instead of the std::string you're passing.

Use std::getline(std::istream&, std::string&, char) instead, like so:

getline(cin, add_string, '\n');

回答2:

istream::getline doesn't take a std::string as parameter, but a char*. You can fix it by calling the function correctly.

So, provided you know the max size of the line:

char buff[256]; //or whatever length
cin.getline (buff,string_size,'\n');
string add_string(buff);

回答3:

Don't use member .getline()s, but global std::getline().

Member .getline()s can only use char * as buffer, while std::getline() can use std::string.

回答4:

cin.getline is a member function. As such, it is not overloaded to account for every possible type in existence. So, developers overload the global version (i.e., std::getline).

来源：https://stackoverflow.com/questions/10625701/how-do-i-fix-a-no-instance-of-overloaded-function-error-with-cin-getline

标签

c++

getline