iOS学习之Delegate设计模式
In review, these are the steps for setting up the delegate pattern between two objects, where object A is the delegate for object B and object B will send out the messages:
1. Define a delegate @protocol for object B.
2. Give object B a property for that delegate protocol.
3. Make object B send messages to its delegate when something interesting happens, such as the user pressing the Cancel or Done buttons, or when it needs a piece of information.
4. Make object A conform to the delegate protocol. It should put the name of the protocol in its @interface line and implement the methods from the protocol.
5. Tell object B that object A is now its delegate.
tips:
1.if screen A(object A) launches screen B(object B) then you don’t want screen B to know too much about the screen that invoked it (A).
3.Anytime you want one part of your app to notify another part about something, usually in order to update the screen, you want to use delegates.
4.if screen A opens screen B, then A can give B the data it needs. You simply make a property for this data on screen B and then screen A puts something into this property right before it makes screen B visible.To pass data back from B to A you would use a delegate.
