Just a quickie note, as a side interest (for fun) I'm trying to get back into Cocoa development (still in newbie stage) and I'm watching the iPhone introductory videos. There's a part of one of the videos related to Cocoa Touch that had me reminded of C# 3.0.

1. Objective-C uses delegates as an alternative to method overrides. I don't recall, outside of callbacks / function pointers, whether C/C++ supported "delegates" in the first place. But the approach taken by Cocoa here really surprised me, how significantly it looked like my Evented Methods pattern [ 1, 2, .. ] I proposed a few days ago, since technically events are just anonymized delegate invocations. Kinda gave me goose bumps, seeing evidence that I was on the right track.
   • On a similar vein, @selector returns a SEL, which is the type name for a selector but the value is just a const char* that is the method name. Selectors are good for invoking methods you don't know the name of until runtime.
     
2. Objective-C has something called "categories", which I feel is a terrible name, but given the description given by the presenter in the video it sounds like Objective-C's categories are functionally the same as C# 3.0's extension methods, although not in form. So, Objective-C supports extension methods, they're just called "Categories", which, again, is a really weird name.
3. It's easy to take C# constructors for granted. In Objective-C, the equivalent functionality is the far less elegant invocation of an "init" method (an initializer).
4. Properties, as being different from methods, functions, and fields, are assumed in Objective-C, as they are in C#. The C# 3.0 compiler supporting the syntax of myType myProp { get; set; } as an inferred implementation of myType _myProp = default(myType); myType myProp { get { return _myProp; } set { _myProp = value; } } is actually not new to C# 3.0, either. While the form is different, Objective-C has something similar. It has a @synthesize keyword that generates the implementation code for the getter and the setter.