NSArray remove last object of type?

Question

Working with an array of UIViews and UIImageViews ([[[UIApplication sharedApplication] window] subviews]). I need to remove only the object of the highest index of the UIImageView type.

NOTE: You need to use an NSMutableArray instead of a NSArray. — Moshe, Feb 03 '12 at 15:37

Sergey Kalinichenko · Answer 1 · 2012-02-03T18:14:51.693

6

You can use indexOfObjectWithOptions:passingTest: method to search the array in reverse for an object that passes a test using a block, and then delete the object at the resulting position:

NSUInteger pos = [myArray indexOfObjectWithOptions:NSEnumerationReverse
                          passingTest:^(id obj, NSUInteger idx, BOOL *stop) {
    return [obj isKindOfClass:[UIImageView class]]; // <<== EDIT (Thanks, Nick Lockwood!)
}];
if (pos != NSNotFound) {
    [myArray removeObjectAtIndex:pos];
}

edited Feb 03 '12 at 18:14

answered Feb 03 '12 at 15:36

Sergey Kalinichenko

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This is a nice solution, but you should compare the type using isKindOfClass instead of ==, otherwise if the UIImageView is actually a subclass of UIImageView it won't work. – Nick Lockwood Feb 03 '12 at 16:26
@NickLockwood That's a nice catch, thank you very much for spotting the problem! – Sergey Kalinichenko Feb 03 '12 at 16:31
1

You also need to add a check that pos != NSNotFound, or it will crash if the array doesn't contain a UIImageView. – Nick Lockwood Feb 03 '12 at 17:50

score 5 · Accepted Answer · edited May 25 '19 at 11:14

5

another block-based solution

[window.subviews enumerateObjectsWithOptions:NSEnumerationReverse 
                                  usingBlock:^(id view, NSUInteger idx, BOOL *stop) 
    {
        if ([view isKindOfClass:[UIImageView class]]){
            [view removeFromSuperview];
            *stop=YES;
    }
}];

non-block solution:

for (UIView *view in [window.subview reverseObjectEnumerator])
{
    if ([view isKindOfClass:[UIImageView class]]){
            [view removeFromSuperview];
            break;
    }
}

I published some demo code, that shows both solutions.

edited May 25 '19 at 11:14

Zoe

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answered Feb 03 '12 at 15:45

vikingosegundo

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These could be improved by removing the view directly inside the loop, then you wouldn't need the viewToRemove variable any more. – Nick Lockwood Feb 03 '12 at 16:22
are you sure? in fast enumeration it is forbidden to alter the array while enumerating. – vikingosegundo Feb 03 '12 at 16:24
@NickLockwood For the reverseObjectEnumerator you are right. but not, if you fast enumerate over the array directly. – vikingosegundo Feb 03 '12 at 16:31
Yeah, true. I forgot you can't safely modify an array while iterating over it. – Nick Lockwood Feb 03 '12 at 16:44
@Kyle I confirmed it myself. see my edit for even prettier code. – vikingosegundo Feb 03 '12 at 17:20

score 3 · Answer 3 · answered Feb 03 '12 at 15:34

3

How about:

UIWindow *window = [[UIApplication sharedApplication] window];
UIView *imageView = nil;
for (UIView *view in window.subviews)
{
    if ([view isKindOfClass:[UIImageView class]])
    {
        imageView = view;
    }
}

//this will be the last imageView we found
[imageView removeFromSuperview];

answered Feb 03 '12 at 15:34

Nick Lockwood

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Well Kyle liked your solution better anyway, so i guess you win, lol ;-) – Nick Lockwood Feb 03 '12 at 16:21
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:) My code usually spends 30 min in front of the mirror every day, to become pretty. – vikingosegundo Feb 03 '12 at 16:22
See my comment above - you can improve it even further. – Nick Lockwood Feb 03 '12 at 16:24
I bow to your dedication to the pursuit of perfection! +1s all round. – Nick Lockwood Feb 03 '12 at 17:47
I am sick at home. I try to eliminate some time. – vikingosegundo Feb 03 '12 at 17:48
I preferred vikingosegundo's solution because it enumerated from the last element to the first. Since I only expect there to be a single other view on the stack following the last UIImageView it might be marginally faster. Your solution was the first one that worked, and had no errors/edits. – Kyle Feb 03 '12 at 18:48

NSArray remove last object of type?

3 Answers3