nsarray

When needing to filter an NSArray to get a subset of the items in the array returned, which method is quicker more frequently and in edge cases? The following tests (compiled in Release mode, executed on a Mac Pro) indicate that filteredArrayUsingPredicate is slower than indexesOfObjectsPassingTest if you use a "textual" predicate, but faster if you use block-based predicate. The fasted method in my test was a simple (fast-enumeration) loop that adds all matching objects to a mutable array. Results for filtering an array of 10,000,000 dictionaries, where about 50% match the predicate: 8.514334

I've been using enumerateObjectsUsingBlock: a lot lately for my fast-enumeration needs, and I'm having a hard time understanding the usage of BOOL *stop in the enumeration block. The NSArray class reference states stop : A reference to a Boolean value. The block can set the value to YES to stop further processing of the array. The stop argument is an out-only argument. You should only ever set this Boolean to YES within the Block. So then of course I can add the following in my block to stop the enumeration: if (idx == [myArray indexOfObject:[myArray lastObject]]) { *stop = YES; } From what I

I am wondering how to convert an NSArray [@"Apple", @"Pear ", 323, @"Orange"] to a string in Objective-C . Dave DeLong NSString * result = [[array valueForKey:@"description"] componentsJoinedByString:@""]; One approach would be to iterate over the array, calling the description message on each item: NSMutableString * result = [[NSMutableString alloc] init]; for (NSObject * obj in array) { [result appendString:[obj description]]; } NSLog(@"The concatenated string is %@", result); Another approach would be to do something based on each item's class: NSMutableString * result = [[NSMutableString

I want to save a Swift Style String Array into NSUserDefaults, but acutally the "if" statement in the code says that returnValue is always nil. Later in the code (iOS 8) I want to use "food += ["spaghetti"] to add new entries. var food : [String] { get { var returnValue : [String]? = NSUserDefaults.standardUserDefaults().objectForKey("food") as? [String] if returnValue == nil //Check for first run of app { returnValue = ["muesli", "banana"]; //Default value } return returnValue! } set (newValue) { NSUserDefaults.standardUserDefaults().setObject(newValue, forKey: "food") NSUserDefaults

What is the difference between copy and mutableCopy when used on either an NSArray or an NSMutableArray ? This is my understanding; is it correct? // ** NSArray ** NSArray *myArray_imu = [NSArray arrayWithObjects:@"abc", @"def", nil]; // No copy, increments retain count, result is immutable NSArray *myArray_imuCopy = [myArray_imu copy]; // Copys object, result is mutable NSArray *myArray_imuMuta = [myArray_imu mutableCopy]; // Both must be released later // ** NSMutableArray ** NSMutableArray *myArray_mut = [NSMutableArray arrayWithObjects:@"A", @"B", nil]; // Copys object, result is immutable