objective C for-loop break and continue

Question

How can i use a 'break' statement within a for-loop which continues form a specified label?

ex;

outer: for(int i = 0;i<[arABFBmatches count];i++){
    for(int i = 0;i<[arABFBmatches count];i++){
        //
        break _____;
    }
}

How to break to outer?

score 110 · Accepted Answer · edited Aug 31 '14 at 18:42

Hard to say from your question. I'd interpret it that you want to skip the rest of the iterations of the inner loop and continue the outer loop?

for (int i = 0; i < [arABFBmatches count]; i++) {
    for (int j = 0; j < [arABFBmatches count]; j++) {
        if (should_skip_rest)
            break; // let outer loop continue iterating
    }
}

Note that I changed the name of your inner loop invariant; using i in both is inviting insanity.

If you want to break from both loops, I wouldn't use a goto. I'd do:

BOOL allDoneNow = NO;
for (int i = 0; i < [arABFBmatches count]; i++) {
    for (int j = 0; j < [arABFBmatches count]; j++) {
        if (should_skip_rest) {
            allDoneNow = YES;
            break;
        }
    }
    if (allDoneNow) break;
}

And please, for the sake of readability, let us not forget to put spaces around our operators. Not "for(int i = 0;i<[arABFBmatches count];i++)". Instead: "for (int i = 0; i < [arABFBmatches count]; i++)" — Erik van der Neut, Jun 20 '14 at 12:19

score 12 · Answer 2 · edited Jun 22 '15 at 20:23

12

Roughly:

for(int i = 0;i<[arABFBmatches count];i++){
    for(int j = 0;j<[arABFBmatches count];j++){
        //
        goto outer_done;
    }
}
outer_done:

Objective-C does not have labelled break.

edited Jun 22 '15 at 20:23

Jeffrey Berthiaume

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answered Jul 14 '10 at 05:25

Matthew Flaschen

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If you're going to use `goto`, be very very very careful that you handle memory management properly. – Dave DeLong Jul 14 '10 at 06:25
`goto` is better than setting a flag and testing the flag to tell whether to break out of the outer loop. sure we must be careful. – neevek Apr 09 '12 at 15:11
4

Not necessarily better at all; if the inner loop is surrounded by some setup/teardown logic, the `goto` may happily jump right over the teardown. If you have to add this kind of logic later, it is easy to forget the short circuit case when refactoring. There is a strong argument to be made for control-flow that is jumpless. – bbum Jan 14 '13 at 03:26
I think that the use of "goto" should be avoided. Apart from bbum's excellent reason, it also hurts readability of the code. – Erik van der Neut Jun 20 '14 at 12:23

score 3 · Answer 3 · edited Mar 04 '16 at 06:25

3

BOOL done = NO;
for(int i = 0;i<[arABFBmatches count] && !done; i++)
{
    for(int i = 0;i<[arABFBmatches count] && !done;i++)
    {
        if (termination condition) 
        {
             // cleanup
             done = YES;
        }
    }
}

edited Mar 04 '16 at 06:25

P.J.Radadiya

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answered Jun 02 '15 at 08:56

drphill

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Can you also add an explanation? – Robert Jun 02 '15 at 09:15

score 3 · Answer 4 · answered Oct 15 '15 at 12:20

From Apple's Objective-C docs:

Objective-C is defined as a small but powerful set of extensions to the standard ANSI C language.

So break and continue can be used wherever they are permitted in C.

continue can be used in looping constructs (for, while and do/while loops).

break can be used in those same looping constructs as well as in switch statements.

score 1 · Answer 5 · edited Sep 15 '16 at 13:32

1

'break' will only get you out of the innermost loop or switch. You can use 'return' to exit out of a function at any time.Please have a look at the this link.

edited Sep 15 '16 at 13:32

Jagat Dave

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answered Feb 26 '14 at 05:19

Suraj K Thomas

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Most commercial design rules demand only one (1) 'return' from a function. – Vincent Mar 10 '16 at 13:43

objective C for-loop break and continue

5 Answers5