ifstream arguments - C++

I Declared: std::string input_file="1.txt";开发者_StackOverflow then I tried to do this command:

static ifstream myfile (input_file);

and I get the error: no matching function for call to : std::basic_ifstream<char>::basic_ifstream(std::string&)

Try:

static ifstream myfile(input_file.c_str());

For some reason, the ifstream constructor doesn't accept an std::string.