Sort by Date: NSArray with NSArray with Date-Object

Question

I have a simple NSArray which has some arrays as objects which has some dates and strings as objects:

NSArray (main array) ---------------> table view
- NSArray (secondary array)---> table view cell
  - NSDate --------------------> table view cell text label
  - NSString -------------------> table view cell detail text label
  - etc.

I use the main array for my table view -> each cell got it's own 'secondary array'. Now I want to sort the main array by the NSDate object. It sounds very easy but I have found no solution on the web for it.

I thought about using NSSortDesriptors but those just sort the array by the objects in the main array and not in the secondary array.

Hopefully you can help me

EDIT: Would it fix the problem if I use a NSDictionary as the secondary array?

Tim Dean · Accepted Answer · 2011-08-10 03:03:26Z

4

You should be able to use NSArray sortedArrayUsingComparator if your app is targeted for iOS 4.0 or later:

NSArray *sortedArray = [mainArray sortedArrayUsingComparator: ^(id obj1, id obj2) {
    return [[obj1 objectAtIndex:0] compare:[obj2 objectAtIndex:0]];
}];

This assumes that the date field is always in index 0 of the internal array. It would probably be a bit cleaner if you used a dictionary and keyed the date field by name, but if you are comfortable with the date field always remaining in index 0 then the above should work.

edited Aug 10, 2011 at 3:03

answered Aug 10, 2011 at 2:58

Tim Dean

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4 Comments

tharkay Over a year ago

I tried your code in SDK 4.3 but I have get the following error: "[__NSCFArray compare:]: unrecognized selector sent to instance"

Tim Dean Over a year ago

I made an update to the code sample right after I posted initially: Any chance you grabbed the previous version instead of the updated one?

tharkay Over a year ago

yes only the previous version of your code resulted in the error code.

tharkay Over a year ago

but it won't work for me ... I think I will change the secondary array into a dictionary that might be easier for me

highlycaffeinated · Accepted Answer · 2011-08-10 03:03:19Z

1

Assuming I've understood your data structure correctly, this should be close:

NSArray *sortedArray = [mainArray sortedArrayUsingComparator:^(id ary1, id ary2) {
    NSArray *array1 = (NSArray *)ary1;
    NSArray *array2 = (NSArray *)ary2;
    NSDate *date1 = (NSDate *)[array1 objectAtIndex:0];
    NSDate *date2 = (NSDate *)[array2 objectAtIndex:0];
    return [date1 compare:date2];
}];

answered Aug 10, 2011 at 3:03

highlycaffeinated

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