CODEWITHSUNDEEP
objective-ccocoansmutablearray
Ben Packard
Ben Packard

Reputation: 26476

Removing object from NSMutableArray

I stumbled across the following shortcut in setting up a for loop (shortcut compared to the textbook examples I have been using):

for (Item *i in items){ ... }

As opposed to the longer format:

for (NSInteger i = 0; i < [items count]; i++){ ... } //think that's right

If I'm using the shorter version, is there a way to remove the item currently being iterated over (ie 'i')? Or do I need to use the longer format?

Upvotes: 16

Views: 49373

Answers (5)

RaiderF
RaiderF

Reputation: 107

Just add keyword break; after removing the item...

for(id item in items) {
    if([item isEqual:itemToDelete]) {
        [items removeObject:item];
        break; // A very important line 🛑
    }
}

Upvotes: 9

slava
slava

Reputation: 9

I use this code for this:

for (NSUInteger i = [items count] - 1; ; i--) {
     [items removeObjectAtIndex:i];
}

Upvotes: 0

serhii
serhii

Reputation: 151

An Objective-C collection must not be modified during enumeration.

You may use this variant to delete objects from collection:

for (NSInteger i = items.count - 1; i >= 0 ; i--) {
   [items removeObjectAtIndex:i];
}

Upvotes: 7

Vladimir
Vladimir

Reputation: 170819

You cannot remove objects from array while fast-enumerating it:

numeration is “safe”—the enumerator has a mutation guard so that if you attempt to modify the collection during enumeration, an exception is raised.

Anyway why do you need to change you container while enumerating it? Consider storing elements that need to be deleted and remove them from your container using removeObjectsInArray: or removeObjectsAtIndexes: method.

Upvotes: 32

BergmannF
BergmannF

Reputation: 10235

The former loop is a "for-each" loop in Objective C.

*i is a pointer to the direct item in the items-Array (most of the time this will be NSMutableArray).

This way you can operate directly on the item:

[items removeObject: i];

This (should) work - I am currently not working on my Mac and can't check it. However it might be that Objective-C Prevents removing objects while iterating over the collection (that is quite common in most languages).

Upvotes: 1

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