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I have used NSSets many times in my apps, but I have never created one myself.
When is it better to use an NSSet as opposed to an NSArray and why?
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Yes, NSArray is faster than NSSet for simply holding and iterating. As little as 50% faster for constructing and as much as 500% faster for iterating.
NSMutableArray and NSArray both are build on CFArray , performance/complexity should be same. The access time for a value in the array is guaranteed to be at worst O(lg N) for any implementation, current and future, but will often be O(1) (constant time).
The NSSet , NSMutableSet , and NSCountedSet classes declare the programmatic interface to an unordered collection of objects. NSSet declares the programmatic interface for static sets of distinct objects. You establish a static set's entries when it's created, and can't modify the entries after that.
arrays can't contain nil.
The image from Apple's Documentation describes it very well:
Array is an ordered (order is maintained when you add) sequence of elements
[array addObject:@1]; [array addObject:@2]; [array addObject:@3]; [array addObject:@4]; [array addObject:@6]; [array addObject:@4]; [array addObject:@1]; [array addObject:@2]; [1, 2, 3, 4, 6, 4, 1, 2] Set is a distinct (no duplicates), unordered list of elements
[set addObject:@1]; [set addObject:@2]; [set addObject:@3]; [set addObject:@4]; [set addObject:@6]; [set addObject:@4]; [set addObject:@1]; [set addObject:@2]; [1, 2, 6, 4, 3] If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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