NSArray +从数组中删除项目

Question

如何从NSArray中删除项目。

Answer 1

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];

Answer 2

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(ie it's autoreleased) remove the release & retain messages

Answer 3

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

Answer 4

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

Answer 5

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;
}

Answer 6

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];
}

Answer 7

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.