1. Chapter Six The Facade Pattern
Ku-Yaw Chang
Assistant Professor, Department of Computer Science and Information Engineering
Da-Yeh University

2. The Object-Oriented Paradigm
Outline
Overview
Introducing the Facade Pattern
Learning the Facade Pattern
Field Notes: The Facade Pattern
Summary
Ku-Yaw Chang
The Object-Oriented Paradigm

3. The Object-Oriented Paradigm
Overview
The Facade Pattern
You have probably implemented in the past
But may not had a name for
In this chapter
What the Facade pattern is and where it is used
The key features of the pattern
Some variations on the Facade pattern
Ku-Yaw Chang
The Object-Oriented Paradigm

4. The Object-Oriented Paradigm
Outline
Overview
Introducing the Facade Pattern
Learning the Facade Pattern
Field Notes: The Facade Pattern
Summary
Ku-Yaw Chang
The Object-Oriented Paradigm

5. Introducing the Facade Pattern
Intent by GoF
Provide a unified interface to a set of interfaces in a sub-system. Facade defines a higher-level interface that makes the subsystem easier to use.
Ku-Yaw Chang
The Object-Oriented Paradigm

6. The Object-Oriented Paradigm
Outline
Overview
Introducing the Facade Pattern
Learning the Facade Pattern
Field Notes: The Facade Pattern
Summary
Ku-Yaw Chang
The Object-Oriented Paradigm

7. Learning the Facade Pattern
Learn how to use a complex system
8 feet of manuals
Ku-Yaw Chang
The Object-Oriented Paradigm

8. Learning the Facade Pattern
4 or 5 people were on a project that needed to use this system
Approach one
All people have to learn the entire thing
Waste everyone’s time
Approach two
Pick one to write routines that the rest of us would use to interface with the system
Create a new class or classes that had interface we required
The rest could use this new interface without having to learn the entire complicated system
Ku-Yaw Chang
The Object-Oriented Paradigm

9. Learning the Facade Pattern
Use a complex system more easily
Use a subset of the system
Use the system in a particular way
Ku-Yaw Chang
The Object-Oriented Paradigm

10. Learning the Facade Pattern
Ku-Yaw Chang
The Object-Oriented Paradigm

11. Learning the Facade Pattern
Ku-Yaw Chang
The Object-Oriented Paradigm

12. The Object-Oriented Paradigm
Outline
Overview
Introducing the Facade Pattern
Learning the Facade Pattern
Field Notes: The Facade Pattern
Summary
Ku-Yaw Chang
The Object-Oriented Paradigm

13. The Object-Oriented Paradigm
Variation One
Reduce the number of objects that a client object must deal with
Ku-Yaw Chang
The Object-Oriented Paradigm

14. Variations Two and Three
Supplement existing functions with new routines
Expand with new functionality
An “encapsulating layer”
Hide or encapsulate the system
Reasons
Track system usage
Swap out system
Ku-Yaw Chang
The Object-Oriented Paradigm

15. The Object-Oriented Paradigm
Outline
Overview
Introducing the Facade Pattern
Learning the Facade Pattern
Field Notes: The Facade Pattern
Summary
Ku-Yaw Chang
The Object-Oriented Paradigm

16. The Object-Oriented Paradigm
Summary
The Facade pattern
Put up a new front in front of the original system
Apply when
Not use all the functionality of a complex system
Encapsulate or hide the original system
Add some new functionality as well
Cost of writing this new class is less
Ku-Yaw Chang
The Object-Oriented Paradigm

17. The End