CODEWITHSUNDEEP
objective-cnsarrayenumeration
malaki1974
malaki1974

Reputation: 1619

For loop or fast enumeration of nsarray with a skip or step

I have an NSArray and I need to perform an action every two items on those two items. So I assume it is like a step value or something like it.

Start the loop, run my command on the first two items and then loop and run my command on the next two items - until the array is exhausted.

Any ideas on how to do this? I thought using a modulus but that can help with even odd, right? I need even and odd every 2.

My code that is hardwired to run on the first two items is below. I would like to add many more items and have the loop intelligently skip every two after the action and start the loop over again.

for (int i = 0; i  < 2; i ++) {
    shut01Path  = CGPathCreateMutable();
    shut01Path = CGPathCreateMutableCopy([self buildPathAtIndex:i].CGPath);
    [arr_cgPathArray addObject:[UIBezierPath bezierPathWithCGPath:shut01Path]];
}

Upvotes: 0

Views: 863

Answers (3)

malaki1974
malaki1974

Reputation: 1619

This code steps for me. Change s as needed. 

int s = [array count]/4;
for (int i = 0; i  < s; i ++) {
    NSLog(@"%i",(i*s));
    NSLog(@"%i",(i*s) + 1);
}

Upvotes: 0

Tricertops
Tricertops

Reputation: 8512

Simply increment the counter by two:

for (NSUInteger i = 0; i  < array.count; i += 2) {
    id even = array[i];
    id odd = array[i + 1]; // Make sure the array has even count, otherwise this crashes.
}

Upvotes: 1

uchuugaka
uchuugaka

Reputation: 12782

You just need to check the index value at the beginning of each iteration of your for-loop. If your index value starts at zero and is incremented by 1 then you can check using modulo If the index % 2 is zero, you've got an even number. Otherwise odd number. Other conditions and indexing schemes may require fancier math or enable other conditional checks.

This is really standard C and general programming.

Upvotes: 0

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