This document discusses design patterns including singleton, facade, composite, and strategy patterns. It provides problems each pattern addresses, UML diagrams for some patterns, and code examples. The document aims to cover these patterns at a high-level to encourage participation and discussion on how to implement them in code.

1. Apex Design Patterns
Created by furuCRM Developer
CreatedDate 2020/11/1

2. What is a design pattern?
• Design patterns represent the best practices used by experienced
object-oriented software developers. Design patterns are solutions
to general problems that software developers faced during
software development. These solutions were obtained by trial and
error by numerous software developers over quite a substantial
period of time.
• Types of Design Patterns
1. Creational Patterns
2. Structural Patterns
3. Behavioral Patterns
• Other reference:S.O.L.I.D

3. The Plan
Cover 4 design patterns
 Problem
 Pattern Abstract(UML)
 Code
Your participation is encouraged!

4. Patterns
1. Singleton
2. Facade
3. Composite
4. Strategy

5. 1.Singleton
 Problem

6. 1.Singleton
 Problem

7. Singleton
• Solution: use singleton
The Singleton pattern attempts to solve the
issue of repeatedly using an object instance, but
only wishing to instantiate it once within a
single transaction context. Common uses for
this pattern include:
1. Global variables - whilst Apex does not
support global variables across
execution contexts, this pattern allows
you to create an object instance that will
only ever be instantiated once within an
execution context.
2. Limiting Impact of Governor Limits

8. 1.Singleton

9. 2. Facade
 Problem and solution
before after

10. 2. Facade
• Pattern Abstract(UML)

11. 2. Facade
• Pattern Abstract(UML)

12. 2. Facade
 Code
 Conclusion
The Facade design pattern increases the maintainability of Apex code by simplifying the
execution of one or complex classes with a facade class.

13. 3. Composite

14. 3.
Composite
 Problem
Boss: I want to add dessert Menu
into diner menu! Right now!!
Me: How to add other menu into
diner menu?

15. 3. Composite
• Solution
• Pattern Abstract(UML)

16. 3. Composite
 Code

17. 4.Strategy
 Problem
What happen? PassengerPlane can fire()??

18. 4.Strategy
 Solution?
1. When I want my plane
can fire by GUN, BOOM,…?
2. I want change plane’s
function at runtime?

19. 4.Strategy
 Solution

20. 4.Strategy
 Code
 Conclusion
The Strategy design pattern uses aggregation instead of inheritance, allowing better
decoupling between the behavior and the class that uses the behavior. This allows the
behavior to be changed without breaking the classes that use it, and the classes can switch
between behaviors by changing the specific implementation used without requiring any
significant code changes.

21. Happy Coding