QString到const std :: string

Question

I want to assign the value in QString to a const std::string

QString qfile("some value");

this is the const std::string variable

const std::string file

The code that I m using

file = qfile.toStdString();

above codes works fine for a normal std::string . But there is some problem because of the keyword 'const'. How do I solve it ?

Answer 1

Don't use the assignment operator to initialize the std::string object but rather initialize the variable directly.

const std::string file = qfile.toStdString();

That aside, please make sure that you're aware of what encoding QString::toStdString() uses; unlike QString , std::string is encoding-agnostic (it's a string of bytes, not characters).

Answer 2

Constants are expressions with a fixed value.

http://www.cplusplus.com/doc/tutorial/constants/

Answer 3

You can also get rid of the const by making copy of the return value of toStdString() :

QString str("text");
std::string std_str(str.toStdString());