gistfile1.m

        self.dataSource = [self.dataSource sortedArrayUsingComparator:^NSComparisonResult(id obj1, id obj2) {
           
            Comment *comment1 = obj1;
            Comment *comment2 = obj2;
            
            if (comment1 == comment2)
            {
                return NSOrderedSame;
            }
            
            // check if both are top level
            
            if (comment1.replyto == nil && comment2.replyto == nil) 
            {
                return [comment1.viewCount compare:comment2.viewCount]*-1;
            }
            else if (comment1.replyto != nil && comment2.replyto == nil)
            {
                Comment *root1 = [self rootComment:comment1];
                
                if (root1 == comment2) 
                {
                    return NSOrderedDescending;
                }
                else 
                {
                    return [root1.viewCount compare:comment2.viewCount]*-1;
                }
            }
            else if (comment1.replyto == nil && comment2.replyto != nil) 
            { 
                Comment *root2 = [self rootComment:comment2];
                
                if (root2 == comment1) 
                {
                    return NSOrderedAscending;
                }
                else 
                {
                    return [comment1.viewCount compare:root2.viewCount]*-1;  
                }
            }
            else 
            {
                Comment *root1 = [self rootComment:comment1];
                Comment *root2 = [self rootComment:comment2];
                
                if (root1 == root2)
                {
                    return [comment1.pubdate compare:comment2.pubdate];
                }
                else 
                {
                    return [root1.viewCount compare:root2.viewCount]*-1;
                }
                
                
            }
            
            return NSOrderedSame;
            
        }];