1. Object Oriented Design Patterns - Behavioral Patterns
IMPORTANT NOTICE TO STUDENTS:
These slides are NOT to be used as a replacement for student notes.
These slides are sometimes vague and incomplete on purpose to spark class discussions.
Object Oriented Design Patterns - Behavioral Patterns
CS 360
Lecture 7

2. Have you ever written code and got the feeling you’ve solved that problem before?
Chances are you probably have!
Write down your solution and
refer to it when needed.
This is the idea of a design pattern.
Design Pattern:
The re-usable form of a software solution.
Optimized using good programming practices.

3. Design Pattern Categories
Design Patterns
Creational
Ways to create objects
Behavioral
How objects interact with each other
Structural
How classes and objects are structured

4. Design Pattern Categories

5. Behavioral Design Patterns
Goal of Behavioral Design Patterns:
Identify common communication patterns between objects.
How responsibilities are split between objects.
More about communication than structure.

6. Behavioral Design Patterns – Template Method
Intent
Define the skeleton of an algorithm in an operation, deferring some responsibilities to subclasses.
lets subclasses redefine certain steps of an algorithm without changing the algorithm's structure.
Consequences
Fundamental technique for code reuse.
Move all common class attributes as high in the class hierarchy as possible.

7. Behavioral Design Patterns – Template Method

8. Behavioral Design Patterns - Iterator
Intent
Allows accessing of elements of a collection in a sequential manner without exposing its internal structure.
Consequences
Supports variations in the traversal of aggregate objects.
Simplify the aggregate’s (list, set, collection) interface.
New aggregate traversal operations can be defined.

9. Behavioral Design Patterns - Observer
Intent
Define a one-to-many dependency between objects so that when one object changes state, all its dependents are notified and updated automatically.
Consequences
Supports loose coupling between objects that interact with each other.
Can be added/removed at any point.
Can add complexity/lead to performance issues if not implemented correctly.

10. Behavioral Design Patterns - Observer

11. Project Group Activity
Search online content for Behavioral Design Patterns implemented using languages for your project.
Template Method
Iterator
Observer