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

Question

I want to use switch-case in my program but the compiler gives me this error:

switch expression of type \'QString\' is illegal

How can I us

Answer 1

This seems a little saner IMHO.

bool isStopWord( QString w ) {
    return (
        w == "the" ||
        w == "at" ||
        w == "in" ||
        w == "your" ||
        w == "near" ||
        w == "all" ||
        w == "this"
    );
}

Answer 2

This has nothing to do with Qt, just as it has nothing to do with the colour of your socks.

C++ switch syntax is as follows:

char c = getc();
switch( c ) {
case 'a':
    a();
    break;
case 'b':
    b();
    break;
default:
    neither();
}

If that doesn't help then please list in detail the error message, possible along with the colour of you socks.

Edit: to respond to your reply, you can't use switch with none-integral types. In particular, you can't use class types. Not objects of type QString and not objects of any other type. You can use an if-else if-else construct instead, or you can use runtime or compile time polymorphism, or overloading, or any of the array of alternatives to a switch.

Answer 3

It is identical to a C++ switch statement.

switch(var){
  case(option1):
      doesStuff();
      break;
  case(option2):
     etc();
     break;
}

Answer 4

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.

Answer 5

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;
}

Answer 6

I would suggest to use if and break. This would make it near to switch case in the computation.

QString a="one"
if (a.contains("one"))
{

   break;
}
if (a.contains("two"))
{

   break;
}