Question

I’ve been trying to logically think about this for a while now and usually I can solve it by writing it out or thinking about it while doing other stuff not associated with programming. However everything I try isn’t working. So basically I have 2 NSArrays, which are both populated from 2 different plists. Each array is filled with all dictionaries: all have the same keys, and all have the same identical structure, but some may have information associated with a key that some don’t. I basically need to check each item in array1 and see if it exists in array2 and if it does NOT exist in array2 then add it to array1 (or array3 seeing how you can’t mutate an array while iterating through it). I need it to see if it exists by a specific key “name_key“.

So… In short my end result needs to be an NSArray with all objects from both arrays without having objects with duplicate names (from the dictionaries name_key).

Below is my actual code that doesn’t work.

IN CODE BELOW: originalWhiskiesListArray = array1
newWhiskiesListArray = array2
combinedWhiskiesListArray = array3 (because you can’t mutate an array while iterating through it.

BOOL whiskyExists = YES;
    for (NSDictionary *newWhisky in newWhiskiesListArray) {

        for (NSDictionary *originalWhisky in originalWhiskiesListArray) {
            NSString * newWhiskyNameString = [[newWhisky objectForKey:NAME_KEY] lowercaseString];
            NSString * origWhiskyNameString = [[originalWhisky objectForKey:NAME_KEY] lowercaseString];

           //Compare lowercase strings and if they don't match then add them to the original plist array.
            if ([newWhiskyNameString isEqualToString:origWhiskyNameString]) {
                whiskyExists = YES;
                break;
            } else {
                whiskyExists = NO;
                break;
                //NSLog(@"Whisky names do not match. New Whisky: %@ Old Whisky: %@",[newWhisky objectForKey:NAME_KEY],[originalWhisky objectForKey:NAME_KEY]);
                //doesn't match so add it
                                }
        }
        if (whiskyExists == NO) {
            [combinedWhiskiesListArray addObject:newWhisky];
            NSLog(@"newWhisky added");
            whiskyExists = YES;
        }

    }

Answer 1

Can either of the whiskey name strings be nil? If so then this breaks the isEqualToString comparison because you can always message nil which returns NO.

Also I believe that the breaks are wrong. You only need to exit the inner loop in case you encounter a match. If not you have to keep going until the end of the inner loop.