Selectors or Blocks for callbacks in an Objective-C library

Question

Question

We\'re developing a custom EventEmitter inspired message system in Objective-C. For listeners to provide callbacks, should we require blocks or selectors and

Answer 1

Personally, I hate using delegates. Because of how objective-C is structured, It really clutters code up If I have to create a separate object / add a protocol just to be notified of one of your events, and I have to implement 5/6. For this reason, I prefer blocks.

While they (blocks) do have their disadvantages (e.x. memory management can be tricky). They are easily extendable, simple to implement, and just make sense in most situations.

While apple's design structures may use the sender-delegate method, this is only for backwards compatibility. More recent Apple APIs have been using blocks (e.x. CoreData), because they are the future of objective-c. While they can clutter code when used overboard, it also allows for simpler 'anonymous delegates', which is not possible in objective C.

In the end though, it really boils down to this: Are you willing to abandon some older, more dated platforms in exchange for using blocks vs. a delegate? One major advantage of a delegate is that it is guaranteed to work in any version of the objc-runtime, whereas blocks are a more recent addition to the language.

As far as NSNotificationCenter/KVO is concerned, they are both useful, and have their purposes, but as a delegate, they are not intended to be used. Neither can send a result back to the sender, and for some situations, that is vital (-webView:shouldLoadRequest: for example).