NSArray + remove item from array

Question

How to remove an item from NSArray.

score 127 · Accepted Answer · edited Jul 22 '14 at 07:17

127

NSArray is not mutable, that is, you cannot modify it. You should take a look at NSMutableArray. Check out the "Removing Objects" section, you'll find there many functions that allow you to remove items:

[anArray removeObjectAtIndex: index];
[anArray removeObject: item];
[anArray removeLastObject];

edited Jul 22 '14 at 07:17

Ja͢ck

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answered Nov 13 '09 at 10:51

luvieere

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Note: [-removeObject:](https://developer.apple.com/library/ios/documentation/cocoa/reference/foundation/classes/NSMutableArray_Class/Reference/Reference.html#//apple_ref/occ/instm/NSMutableArray/removeObject:) removes **all matching occurrences** in the array. – Pang Mar 13 '14 at 09:17

score 24 · Answer 2 · answered Nov 13 '09 at 11:37

NSMutableArray *arrayThatYouCanRemoveObjects = [NSMutableArray arrayWithArray:your_array];

[arrayThatYouCanRemoveObjects removeObjectAtIndex:your_object_index];

[your_array release];

 your_array = [[NSArray arrayWithArray: arrayThatYouCanRemoveObjects] retain];

that's about it

if you dont own your_array(i.e it's autoreleased) remove the release & retain messages

score 20 · Answer 3 · edited Dec 28 '16 at 21:35

20

This category may be to your taste. But! Be frugal with its usage; since we are converting to a NSMutableArray and back again, it's not at all efficient.

@implementation NSArray (mxcl)

- (NSArray *)arrayByRemovingObject:(id)obj
{
    if (!obj) return [self copy]; // copy because all array* methods return new arrays
    NSMutableArray *mutableArray = [NSMutableArray arrayWithArray:self];
    [mutableArray removeObject:obj];
    return [NSArray arrayWithArray:mutableArray];
}

@end

edited Dec 28 '16 at 21:35

Adem

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answered Nov 26 '10 at 16:09

mxcl

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you're a champion! I had to use the above method because I sort an NSMutableArray, which means that the array I use in my table cells is not mutable. Therefore when I go to remove objects from the array I use your method to do so. – gotnull Feb 06 '11 at 10:34

score 18 · Answer 4 · answered May 06 '14 at 09:35

18

Here's a more functional approach using Key-Value Coding:

@implementation NSArray (Additions)

- (instancetype)arrayByRemovingObject:(id)object {
    return [self filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:@"SELF != %@", object]];
}

@end

answered May 06 '14 at 09:35

Rudolf Adamkovič

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Elegant. May not perform as fast as the other solutions, however. Be sure to test this with large datasets if that's what you're dealing with. – Thomas Tempelmann May 05 '19 at 13:54

score 4 · Answer 5 · edited Jul 04 '14 at 06:29

4

Made a category like mxcl, but this is slightly faster.

My testing shows ~15% improvement (I could be wrong, feel free to compare the two yourself).

Basically I take the portion of the array thats in front of the object and the portion behind and combine them. Thus excluding the element.

- (NSArray *)prefix_arrayByRemovingObject:(id)object 
{
    if (!object) {
        return self;
    }

    NSUInteger indexOfObject = [self indexOfObject:object];
    NSArray *firstSubArray = [self subarrayWithRange:NSMakeRange(0, indexOfObject)];
    NSArray *secondSubArray = [self subarrayWithRange:NSMakeRange(indexOfObject + 1, self.count - indexOfObject - 1)];
    NSArray *newArray = [firstSubArray arrayByAddingObjectsFromArray:secondSubArray];

    return newArray;
}

edited Jul 04 '14 at 06:29

Ossir

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answered Dec 11 '13 at 21:03

jmathew

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`NSArray* newArray = [NSArray array];` initialization here is redundant – Ossir Apr 24 '14 at 14:14
1

@Ossir You're right the declaration is redundant because the `[self subarray...]` part. @Michael Ozeryansky, if the obj is nil `indexOfObject` will return `NSNotFound`. I'm not sure what happens then but its probably not the right thing, thanks! – jmathew Jun 02 '14 at 15:27

score 4 · Answer 6 · answered Oct 21 '14 at 21:38

Remove Object from NSArray with this Method:

-(NSArray *) removeObjectFromArray:(NSArray *) array withIndex:(NSInteger) index {
    NSMutableArray *modifyableArray = [[NSMutableArray alloc] initWithArray:array];
    [modifyableArray removeObjectAtIndex:index];
    return [[NSArray alloc] initWithArray:modifyableArray];
}

score 0 · Answer 7 · answered Apr 19 '19 at 15:34

As others suggested, NSMutableArray has methods to do so but sometimes you are forced to use NSArray, I'd use:

NSArray* newArray = [oldArray subarrayWithRange:NSMakeRange(1, [oldArray count] - 1)];

This way, the oldArray stays as it was but a newArray will be created with the first item removed.

NSArray + remove item from array

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