switch/case statement in C++ with a QString type

How can I use the switch statement with a QString?

You can't. In C++ language switch statement can only be used with integral or enum types. You can formally put an object of class type into a switch statement, but that simply means that the compiler will look for a user-defined conversion to convert it to integral or enum type.

You can, creating an QStringList before iteration, like this:

QStringList myOptions;
myOptions << "goLogin" << "goAway" << "goRegister";

/*
goLogin = 0
goAway = 1
goRegister = 2
*/

Then:

switch(myOptions.indexOf("goRegister")){
  case 0:
    // go to login...
    break;

  case 1:
    // go away...
    break;

  case 2:
    //Go to Register...
    break;

  default:
    ...
    break;
}