iOS break loop with switch

Question

I have a loop like this:

label: for(X *y in z)
    {
        switch(y.num)
        {
          case ShouldDoSomething:
            [self somethingWithX:y];
            break;
          case ShouldStopNow:
            y = [self valWhenStopped];
            break label;
        }
        [val append y];
    }

Of course, since Objective-C does not support loop labeling (at least, when I try, it throws a compile error saying Expected ';' after break statement), this doesn't work. Is there a way I can break a loop using a switch case in Objective-C? If not, what's a best practice with the same effect?

you can use "`goto` + label", [but do you really want to do it](http://stackoverflow.com/questions/1764354/how-can-i-use-goto-in-a-switch-statement-in-objective-c)? — Michael Dautermann, Jun 26 '15 at 18:23

vadian · Accepted Answer · 2015-06-27T04:38:40.873

4

A solution is to put the whole expression into a method and exit the switch statement with return.

- (void)checkSomething:(id)object
{
  for(X *y in object)
  {
    switch(y.num)
    {
      case ShouldDoSomething:
        something();
        break;
      case ShouldStopNow:
        return;
        break;
    }
    somethingElse();
  }
}

Another solution is using a boolean flag

for(X *y in Z)
  {
    BOOL willExitLoop = false;
    switch(y.num)
    {
      case ShouldDoSomething:
        something();
        break;
      case ShouldStopNow:
        willExitLoop = true;
        break;
    }
    if (willExitLoop) break;
    somethingElse();
  }

edited Jun 27 '15 at 04:38

answered Jun 26 '15 at 18:23

vadian

274,689
30
353
361

This seems like two solutions in one answer. Perhaps split them into two answers? – Ky - Jun 26 '15 at 18:29
I changed the formatting of the answer to make it clearer – vadian Jun 26 '15 at 18:32
1

You still center your answer around using a method and return, but don't provide code. And then you somewhat passively say there's another solution, and provide code for that. – Ky - Jun 26 '15 at 18:33
I edited the code to reflect your main answer. I hope you don't mind. – Ky - Jun 26 '15 at 21:48
and I edited my post to provide code for the first solution and I changed the code of the second solution because it didn't work as you requested – vadian Jun 27 '15 at 04:42

score 1 · Answer 2 · answered Jun 26 '15 at 18:31

1

You can also use a flag:

for(...)
{
    BOOL stop = NO ;
    switch(...)
    {
        case x:
            break ;
        case y:
            stop = YES ;
            break ;
    }
    if ( stop ) { break ; }
    somethingElse();
}

answered Jun 26 '15 at 18:31

nielsbot

15,922
4
48
73

score 1 · Answer 3 · answered Jun 26 '15 at 20:37

1

I think you are looking for continue:

for(X *y in Z)
{
switch(y.num)
{
    case ShouldDoSomething:
        something();
        break;
    case ShouldStopNow:
        continue;  //-- this will break the switch and reenter the for loop with the next element
}
somethingElse();
}

answered Jun 26 '15 at 20:37

sergio

68,819
11
102
123

Except that will continue looping, perhaps 1 or more times. I wish to stop looping altogether. – Ky - Jun 26 '15 at 21:43

iOS break loop with switch

3 Answers3