Sort Array of Dictionaries by NSDate

Question

I have an array of dictionaries. Within each dictionary, there is a a key dateOfInfo (an NSDate) and several other things. I want to sort the array by each dictionaries dateOfInfo with the most recent being the first result.

How can I do this?

Answer 1

You can sort using NSSortDescription, e.g.

NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey: @"dateOfInfo" ascending: NO];
NSArray *sortedArray = [array sortedArrayUsingDescriptors:[NSArray arrayWithObject:sortDescriptor]];
[sortDescriptor release];

You can also use the method

- (NSArray *)sortedArrayUsingFunction:(NSInteger (*)(id, id, void *))comparator context:(void *)context

Answer 2

The basic bubble sorting algorithm would work. In this case you need to loop through your array, use valueForKey message on [array objectAtIndex:] to get the NSDate values. For comparing dates see this post . So if you are sorting in ascending order of date, just add the object with the lower date (remember bubble sort comparisons?) to an array which will hold your sorted result.