for (NSString* key in xyz) { id value = xyz[key]; // do stuff } This works for every class that conforms to the NSFastEnumeration protocol (available on 10.5+ and iOS), though NSDictionary is one of the few collections which lets you enumerate keys instead of values. I suggest you read about fast enumeration in the … Read more
NSMutableDictionary isn’t designed to be thread-safe data structure, and simply marking the property as atomic, doesn’t ensure that the underlying data operations are actually performed atomically (in a safe manner). To ensure that each operation is done in a safe manner, you would need to guard each operation on the dictionary with a lock: // … Read more
The NSDictionary and NSMutableDictionary docs are probably your best bet. They even have some great examples on how to do various things, like… …create an NSDictionary NSArray *keys = [NSArray arrayWithObjects:@”key1″, @”key2″, nil]; NSArray *objects = [NSArray arrayWithObjects:@”value1″, @”value2″, nil]; NSDictionary *dictionary = [NSDictionary dictionaryWithObjects:objects forKeys:keys]; …iterate over it for (id key in dictionary) { … Read more
Get the Array of the Values, sort that array and then get the key corresponding to the value. You can get the values with: NSArray* values = [myDict allValues]; NSArray* sortedValues = [values sortedArrayUsingSelector:@selector(comparator)]; But, if the collection is as you show in your example, (I mean, you can infer the value from the key), … Read more
A couple of years ago, I wrote a few category methods for exactly the same reason, transforming a whole tree of user defaults to mutable. Here they are – use them at your own risk! 🙂 // // SPDeepCopy.h // // Created by Sherm Pendley on 3/15/09. // #import <Cocoa/Cocoa.h> // Deep -copy and -mutableCopy … Read more
setValue:forKey: is part of the NSKeyValueCoding protocol, which among other things, lets you access object properties from the likes of Interface Builder. setValue:forKey: is implemented in classes other than NSDictionary. setObject:forKey: is NSMutableDictionary’s reason to exist. Its signature happens to be quite similar to setValue:forKey:, but is more generic (e.g. any key type). It’s somewhat … Read more