nsarray

Non-retaining array for delegates

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I found this bit of code awhile ago (can’t remember who to attribute it to). It’s quite ingenius, using a Category to allow the creation of a mutable array that does no retain/release by backing it with a CFArray with proper callbacks. @implementation NSMutableArray (WeakReferences) + (id)mutableArrayUsingWeakReferences { return [self mutableArrayUsingWeakReferencesWithCapacity:0]; } + (id)mutableArrayUsingWeakReferencesWithCapacity:(NSUInteger)capacity { … Read more

How do I remove leading & trailing whitespace of NSString inside an NSArray?

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The NSArray and the contained NSString objects are all immutable. There’s no way to change the objects you have. Instead you have to create new strings and put them in a new array: NSMutableArray *trimmedStrings = [NSMutableArray array]; for (NSString *string in arrayRefineSubjectCode) { NSString *trimmedString = [string stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]]; [trimmedStrings addObject:trimmedString]; } arrayRefineSubjectCode = … Read more

Convert NSArray to NSDictionary

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Try this magic: NSDictionary *dict = [NSDictionary dictionaryWithObjects:records forKeys:[records valueForKey:@”intField”]]; FYI this is possible because of this built-in feature: @interface NSArray(NSKeyValueCoding) /* Return an array containing the results of invoking -valueForKey: on each of the receiver’s elements. The returned array will contain NSNull elements for each instance of -valueForKey: returning nil. */ – (id)valueForKey:(NSString *)key;

NSArray + remove item from array

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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];

Finding smallest and biggest value in NSArray of NSNumbers

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If execution speed (not programming speed) is important, then an explicit loop is the fastest. I made the following tests with an array of 1000000 random numbers: Version 1: sort the array: NSArray *sorted1 = [numbers sortedArrayUsingSelector:@selector(compare:)]; // 1.585 seconds Version 2: Key-value coding, using “doubleValue”: NSNumber *max=[numbers valueForKeyPath:@”@max.doubleValue”]; NSNumber *min=[numbers valueForKeyPath:@”@min.doubleValue”]; // 0.778 seconds … Read more

Static NSArray of strings – how/where to initialize in a View Controller

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Write a class method that returns the array. + (NSArray *)titles { static NSArray *_titles; static dispatch_once_t onceToken; dispatch_once(&onceToken, ^{ _titles = @[@”Your Move”, @”Their Move”, @”Won Games”, @”Lost Games”, @”Options”]; }); return _titles; } Then you can access it wherever needed like so: NSArray *titles = [[self class] titles];