Streamline Your App with Design Patterns:

1.A Design Pattern Is a Template for a Design That Solves a Programming Problem.

2.The Most Important Design Pattern: Model-View-Controller.

3.Solving Problems with Design Patterns:

a.Delegation: Acting on Behalf of Another (Framework) Object.

b.Protocol: Enabling Communication Between Objects Not Related by Inheritance.

c.Notification Center: Notifying Interested Observers of an Event.

d.Target-Action: Encapsulating a Message to Be Sent When an Event Occurs.

e.Key-Value Observing: Notifying an Observer When a Value Changes.

f.Other Framework Designs Based on Design Patterns:

(1).View hierarchy.

(2).Responder chain.

(3).View controller.

(4).Receptionist.