Seymour Cakes Seymour Cakes - 5 months ago 29
iOS Question

The best way to remove duplicate values from NSMutableArray in Objective-C?

The best way to remove duplicate values (NSString) from

NSMutableArray
in Objective-C?

Is this the easiest and right way to do it?

uniquearray = [[NSSet setWithArray:yourarray] allObjects];

Answer

Your NSSet approach is the best if you're not worried about the order of the objects, but then again, if you're not worried about the order, then why aren't you storing them in an NSSet to begin with?

I wrote the answer below in 2009; in 2011, Apple added NSOrderedSet to iOS 5 and Mac OS X 10.7. What had been an algorithm is now two lines of code:

NSOrderedSet *orderedSet = [NSOrderedSet orderedSetWithArray:yourArray];
NSArray *arrayWithoutDuplicates = [orderedSet array];

If you are worried about the order and you're running on iOS 4 or earlier, loop over a copy of the array:

NSArray *copy = [mutableArray copy];
NSInteger index = [copy count] - 1;
for (id object in [copy reverseObjectEnumerator]) {
    if ([mutableArray indexOfObject:object inRange:NSMakeRange(0, index)] != NSNotFound) {
        [mutableArray removeObjectAtIndex:index];
    }
    index--;
}
[copy release];
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