CODEWITHSUNDEEP
iosnsmutablearray
Malloc
Malloc

Reputation: 16286

"Incompatible pointer type.." when trying to sort using `sortedArrayUsingFunction`

I am trying to sort an NSMutableArray of NSMutableDictionarys basing on a price field.

NSString* priceComparator(NSMutableDictionary *obj1, NSMutableDictionary *obj2, void *context){

    return @"just for test for the moment";

}

//In other function
arrayProduct = (NSMutableArray*)[arrayProduct sortedArrayUsingFunction:priceComparator context:nil];//arrayProduct is NSMutableArray containing NSDictionarys

On the statement above, I am getting the following warning which I want to fix:

Incompatible pointer types sending 'NSString*(NSMutableDictionary *__strong,NSMutableDictionary *__strong,void*)' to parameter of type 'NSInteger (*)(__strong id, __strong id, void*)'

Upvotes: 1

Views: 268

Answers (1)

Mike Mertsock
Mike Mertsock

Reputation: 12025

As the error states, your priceComparator function needs to be declared as returning NSInteger, not NSString *:

NSInteger priceComparator(NSMutableDictionary *obj1, NSMutableDictionary *obj2, void *context){
    if (/* obj1 should sort before obj2 */)
        return NSOrderedAscending;
    else if (/* obj1 should sort after obj2 */)
        return NSOrderedDescending;
    else
        return NSOrderedSame;
}

Better yet, you could use NSSortDescriptors if the price you need to sort by is a simple numeric value that's always at a given key in these dictionaries. I think this is the syntax:

id descriptor = [NSSortDescriptor sortDescriptorWithKey:@"price" ascending:YES];
NSArray *sortedProducts = [arrayProduct sortedArrayUsingDescriptors:@[descriptor]];

Also note that all of the sortedArray... methods return a new, plain NSArray object, not a NSMutableArray. Thus the sortedProducts declaration in the sample code above. If you really do need your sorted array to still be mutable, you could use the sortUsingFunction:context: or sortUsingDescriptors: method of NSMutableArray to sort the array in-place. Note that these methods return void, so you wouldn't assign the result to any variable, it would modify your arrayProduct object in-place.

Upvotes: 4

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