The synthesized setter for @property (copy) sends a copy message to the array, which results in an immutable copy. You have no choice but the implement the setter yourself here, as detailed in the Objective-C guide.
Just convert the array to an NSSet and back again. A set can’t have duplicates by design. EDIT: Note that a set doesn’t have a sorting order. Therefore, you can go cheaper and forgo the order, or go for a slightly more expensive operation but keep the order. NSArray *hasDuplicates = /* (…) */; NSArray … Read more
Matt Gallagher has written a pretty informative article on Cocoa’s collection classes, along with a couple of benchmarks (with & without initWithCapacity:, as well as cross class comparisons) http://cocoawithlove.com/2008/08/nsarray-or-nsset-nsdictionary-or.html His test (source available) for an NSMutableArray of length 1,000,000 took 0.582256sec without capacity and just 0.572139sec with capacity. Test | Time [NSMutableArray array] | 0.582256 … Read more
You can use NSMutableArray‘s removeObjectIdenticalTo: method, as follows [mutArrSkills removeObjectIdenticalTo:[NSNull null]]; to remove the null values. No need to iterate.
First, you must allocate and initialize your objects before use, something like: NSMutableArray * sections = [[NSMutableArray alloc] initWithCapacity:10]; For the rows, you need one object for each, not a single NSMutableArray * rows; Second, depending on whether you’re using Xcode 4.4+ (which introduced subscripting, a.k.a section[i] & section[i] = …) you may have to … Read more
NSArray *array = @[@{@”groupId” : @”1″, @”name” : @”matt”}, @{@”groupId” : @”2″, @”name” : @”john”}, @{@”groupId” : @”3″, @”name” : @”steve”}, @{@”groupId” : @”4″, @”name” : @”alice”}, @{@”groupId” : @”1″, @”name” : @”bill”}, @{@”groupId” : @”2″, @”name” : @”bob”}, @{@”groupId” : @”3″, @”name” : @”jack”}, @{@”groupId” : @”4″, @”name” : @”dan”}, @{@”groupId” : @”1″, @”name” … Read more
Use NSMutableSet: NSMutableSet *intersection = [NSMutableSet setWithArray:array1]; [intersection intersectSet:[NSSet setWithArray:array2]]; [intersection intersectSet:[NSSet setWithArray:array3]]; NSArray *array4 = [intersection allObjects]; The only issue with this is that you lose ordering of elements, but I think (in this case) that that’s OK. As has been pointed out in the comments (thanks, Q80!), iOS 5 and OS X 10.7 … Read more
You can always iterate without an enumerator. Which means a regular for loop, and when you remove an object:- decrement the index variable and continue;. if you are caching the array’s count before entering the for-loop, then make sure you decrement that too when removing an object. Anyway, I do not see why an array … Read more
Copy on write is a tricky thing, and you need to think carefully about how many things are sharing a structure that you’re trying to modify. The culprit is here. countToColorMap[colorCount]?.append(CountedColor(color: color as! UIColor, colorCount: colorCount)) This is generating a temporary value that is modified and put back into the dictionary. Since two “things” are … Read more
copy and mutableCopy are defined in different protocols (NSCopying and NSMutableCopying, respectively), and NSArray conforms to both. mutableCopy is defined for NSArray (not just NSMutableArray) and allows you to make a mutable copy of an originally immutable array: // create an immutable array NSArray *arr = [NSArray arrayWithObjects: @”one”, @”two”, @”three”, nil ]; // create … Read more