Array comparison failing for copied items

Question

I am trying to compare two mutable arrays having my model objects. In one array I am creating the model objects as-is, where as in the other array I am creating a copy of the original object using copyWithZone (My models are subclass of NSObject). However when I compare, It is always failing even though I did not change anything.

I printed both the arrays just to check and both seem to have the same objects.

Will isEqualToArray not work on copied items?

Can someone point out where I am going wrong? Or if there is any other way to do this comparison?

Answer 1

When comparison involved between object, then isEqual and hash methods should be overridden. isEqualToArray will return true only if object pass isEqual test. So please implement isEqual and hash methods in your modal object. After that you will able to use isEqualToArray method.

Answer 2

I suggest for you to override the isEqual: method on both NSObject subclasses in a format similar to the example below.

Assume there is object of class Object and Compared Object. Both contain properties called propA (nsnumber) and propB (nsstring). This will work even if the two objects are of the same subclass.

-(BOOL)isEqual:(id)object {
    if ([object isKindOfClass:[ComparedObject class]]) {
        if ([self.propA isEqualToNumber:object.propA] && [self.propB             
            isEqualToString:object.propB]) {
            return YES;
        }
    }
    return NO;
}

Then, you can simply iterate through the contents of the arrays and check each object in the example method shown below.

- (BOOL) isArrayEqual:(NSMutableArray *)fArray compareTo:(NSMutableArray *)sArray {
    for (CustomObject *obj in fArray) {
        NSUInteger index = [fArray indexOfObject:obj];
        if (![obj isEqual:[sArray objectAtIndex:index]]) {
            return NO;
        }
    }
    return YES;
}