Convert MFC CString to integer

Question

How to convert a CString object to integer in MFC.

Answer 1

The canonical solution is to use the C++ Standard Library for the conversion. Depending on the desired return type, the following conversion functions are available: std::stoi, std::stol, or std::stoll (or their unsigned counterparts std::stoul, std::stoull).

The implementation is fairly straight forward:

int ToInt( const CString& str ) {
    return std::stoi( { str.GetString(), static_cast( str.GetLength() ) } );
}

long ToLong( const CString& str ) {
    return std::stol( { str.GetString(), static_cast( str.GetLength() ) } );
}

long long ToLongLong( const CString& str ) {
    return std::stoll( { str.GetString(), static_cast( str.GetLength() ) } );
}

unsigned long ToULong( const CString& str ) {
    return std::stoul( { str.GetString(), static_cast( str.GetLength() ) } );
}

unsigned long long ToULongLong( const CString& str ) {
    return std::stoull( { str.GetString(), static_cast( str.GetLength() ) } );
}

All of these implementations report errors through exceptions (std::invalid_argument if no conversion could be performed, std::out_of_range if the converted value would fall out of the range of the result type). Constructing the temporary std::[w]string can also throw.

The implementations can be used for both Unicode as well as MBCS projects.