Question

I need so sort an array with an array inside, something like this:

 NSMutableArray * array_example = [[NSMutableArray alloc] init];

 [array_example addObject:[NSMutableArray arrayWithObjects:
                            string_1,
                            string_2,
                            string_3,
                            nil]
 ];

how can i order this array by the field “string_1” of the array???
any idea how can i do that?

Thanks

Answer 1

For iOS 4 and later, this is easily done using a comparator block:

[array_example sortUsingComparator:^(NSArray *o1, NSArray *o2) {
    return (NSComparisonResult)[[o1 objectAtIndex:0] compare:[o2 objectAtIndex:0]];
}];

If you’re interested in how blocks work, you can have a look at Apple’s Short Practical Guide to Blocks.

If you wish to support iOS 3.x, you’d have to use a custom comparison function:

NSComparisonResult compareArrayFirstElement(NSArray *o1, NSArray *o2) {
    return [[o1 objectAtIndex:0] compare:[o2 objectAtIndex:0]];
}

and then use:

[array_example sortUsingFunction:compareArrayFirstElement context:nil];