Question

I have an array of dictionaries.
Each dictionary is like this

object, @"myObject",
[NSValue valueWithCGRect:myRect], @"rect",
nil

How do I sort that array by myRect.origin.x ?

I know that objective-c has smart ways to sort arrays of dictionaries. My problem here is that I want to sort by the x coordinate of myRect and myRect is wrapped in a NSValue… any way to do that with a magic command? I know you guys are magicians! 😀

thanks.

Answer 1

The cleanest way is probably to use a method like sortUsingComparator: or sortedArrayUsingComparator (depending on the mutability of the array) and define a custom comparator (a block taking two parameters and returning an NSComparisonResult) that unpacks your rects and compare their x-coordinates.

edit: Well, since everyone else is providing code, here’s mine:

[array sortUsingComparator:^NSComparisonResult(id obj1, id obj2) {
    CGRect rect1 = [[obj1 valueForKey:@"rect"] CGRectValue];
    CGRect rect2 = [[obj2 valueForKey:@"rect"] CGRectValue];

    if(rect1.origin.x < rect2.origin.x) {
        return NSOrderedAscending;
    } else if(rect1.origin.x > rect2.origin.x) {
        return NSOrderedDescending;
    } else {
        return NSOrderedSame;
    }
}];