[Zev]

A lot of Apple stuff may be a black box but it is designed to be subclassed.

Aside from a small number of top-level classes[1] UIKit isn't designed to be subclassed. When you subclass things like UIAlertView, UIButton, UISwitch, UITextField, UIWebView… etc, you're in for a world undocumented gotchas and spending hours to do small simple things.

1. UIView, UIControl, UITableViewCell, UIScrollView, UIGestureRecognizer, UIViewController, UIApplication and maybe one or two other classes.

[reidmain]

And you've listed about 90% of the things I usual end up subclassing because I've hit some limitation.

Also I wasn't talking specifically about UIKit. Foundation is another great framework that I've subclassed many times.

It's not perfect but Apple puts a lot of work into documenting how to subclass their frameworks. Third-party UI frameworks like this are much less forgiving.

[Zev]

Can you give an example of some things that you subclass?

[reidmain]

From Foundation? NSDictionary, NSArray and NSOperation instantly jump to mind.

[Zev]

What do you get out of subclassing NSDictionary or NSArray that you don't get out of a category?

[reidmain]

Well in this case I subclassed them so I could have the backing data source only weakly reference the items in the dictionary/array and because I subclassed them I can use them wherever NSDictionary or NSArray is an accepted parameter.

Apple's documentation also gives some examples:

https://developer.apple.com/library/ios/#documentation/Cocoa...

https://developer.apple.com/library/ios/#documentation/Cocoa...

[Zev]

Why not use CFDictionaryRef and pass it along via toll-free bridging?