How to sort NSPredicate

Question

I am trying to sort my array while using NSPredicate.. I have read other places that possibly using NSSortDescriptor could be an option. Having some trouble figuring this out.

I am attempting to sort my array by companyName.

Any advice appreciated, thanks

Greg

- (void)filterSummaries:(NSMutableArray *)all byNameThenBooth:(NSString*) text results:(NSMutableArray *)results
{
    [results removeAllObjects];

    if ((nil != text) && (0 < [text length])) {        
        if ((all != nil) && (0 < [all count])) {
            NSPredicate *predicate = [NSPredicate predicateWithFormat: @"companyName contains[cd] %@ OR boothNumber beginswith %@", text, text];
            [results addObjectsFromArray:[all filteredArrayUsingPredicate:predicate]];        
        }
    }
    else {
        [results addObjectsFromArray:all];
    }
}

Answer 1

you have several options how to sort an array:

I'll show a NSSortDescriptor-based approach here.

NSPredicate *predicate = [NSPredicate predicateWithFormat:
                                  @"companyName contains[cd] %@ OR boothNumber beginswith %@",
                                  text,
                                  text];

// commented out old starting point :)
//[results addObjectsFromArray:[all filteredArrayUsingPredicate:predicate]];

// create a descriptor
// this assumes that the results are Key-Value-accessible
NSSortDescriptor *descriptor = [NSSortDescriptor sortDescriptorWithKey:@"companyName" 
                                                             ascending:YES];
//
NSArray *results = [[all filteredArrayUsingPredicate:predicate]  
                     sortedArrayUsingDescriptors:[NSArray arrayWithObject:descriptor]];

// the results var points to a NSArray object which contents are sorted ascending by companyName key

This should do your job.

Answer 2

The filteredArrayUsingPredicate: function walks through your array and copies all objects that match the predicate into a new array and returns it. It does not provide any sorting whatsoever. It's more of a search.

Use the sorting functions of NSArray, namely sortedArrayUsingComparator:, sortedArrayUsingDescriptors:, sortedArrayUsingFunction:context: and the like, whichever serves you most.

Checkout NSArray Class Reference for details.

BTW: If you want to sort lexically, you may use sortedArrayUsingSelector:@selector(compare:) which will use NSString's compare: function to find the right order.