Is there a way to iterate over an dictionary?

Question

I know dictionaries as something where you need a key in order to get a value. But what would I do, when I need to iterate over all keys and values in that dictionary so that I know what keys are there, and what values are there? Is that possible to do? I know in JavaScript there's something called for-in-loop. But in objective-c / cocoa-touch?

Answer 1

Yes, NSDictionary supports fast enumeration. With Objective-C 2.0, you can do this:

// To print out all key-value pairs in the NSDictionary myDict
for(id key in myDict)
    NSLog(@"key=%@ value=%@", key, [myDict objectForKey:key]);

The alternate method (which you have to use if you're targeting Mac OS X pre-10.5, but you can still use on 10.5 and iPhone) is to use an NSEnumerator:

NSEnumerator *enumerator = [myDict keyEnumerator];
id key;
// extra parens to suppress warning about using = instead of ==
while((key = [enumerator nextObject]))
    NSLog(@"key=%@ value=%@", key, [myDict objectForKey:key]);