Q:

id<>delegate what is the meaning of this syntax?

I don't know what does this mean?I think this is related to protocol,but can someone tell me what is the correct meaning of this kind of syntax?
id<aKeypadDelegate> delegate;

A:

id is a reference to a Objective-C object whose class is unknown, hence delegate can be any Objective-C object.
When you find this:
@property (nonatomic, weak) id<SomeProtocolHere> delegate;

...it means that delegate can be any kind of Objective-C object that implements ("conforms to") SomeProtocolHere protocol.

