How can I break out of two nested for loops in Objective-C?

Question

I have two for loops nested like this:

for(...) {
    for(...) {

    }
}

I know that there is a break statement. But I am con

Answer 1

Probably the easiest way is to use a "flag" variable

for(i=0; i<10 && (done==false); i++)
  for(j=0;j< 10; j++){
     ..
     ..
     if(...){done=true; break;}
  }

Answer 2

Others have mentioned how you can set a flag or use a goto, but I'd recommend refactoring your code so that the inner loop is turned into a separate method. That method can then return some flag to indicate that the outer loop should break. If you name your methods appropriately, this is much more readable.

for (int i = 0; i < 10; i++) {
   if (timeToStop(i)) break;
}

-(bool) timeToStop: (int) i {
    for (int j = 0; j < 10; j++) {
        if (somethingBadHappens) return true;
    }

    return false;
}

Pseudocode, not tested, but you get the idea.

Answer 3

Another solution is to factor out the second loop in a function:

int i;

for(i=0; i<10 ; i++){
    if !innerLoop(i) {
        break;
    }
}

bool innerLoop(int i)
    int j;
    for(j=0;j< 10; j++){
        doSomthing(i,j);
        if(endcondtion){
            return false;
        }
    }
}

Answer 4

break breaks out of one loop, but you can add a check to the outer loop which breaks when the inner breaks.

bool dobreak = false;
for ( ..; !dobreak && ..; .. ) {
   for ( ... ) {
      if (...) {
         dobreak = true;
         break;
      }
   }
}

Answer 5

The break statement only gets you out of the innermost loop. If you don't want the added overhead in code, memory and performance of a dedicated state variable, I recommend refactoring the code out into a function or method of its own, and using return to get out of all the loops:

void do_lots_of_work(void)
{
  int i, j;

  for(i=0; i<10 ; i++)
  {
    for(j=0;j< 10; j++)
    {
     ..
     ..
     if(disaster_struck())
      return; /* Gets us out of the loops, and the function too. */
    }
  }
}

Answer 6

The break statement breaks out of the innermost loop. An additional test and break statement would be needed to break out of the outer loop.