Part 1 of Apex Design Patterns in Salesforce

1. Path to Code
Begin Your Salesforce Coding Adventure

2. Episode 21
Design Pattern - Part 1

3. Jitendra Zaa
Salesforce MVP
Sr Technical Architect
23x Certified
@Jitendra Zaa
Speaker

4. Agenda
• SOLID
• Design Principles
• What are design Patterns
• Who are Gang Of Four
• GoF Patterns
• Creational Pattern
• Example

5. Some House Rules
• Please mute your mic
• Keep adding questions in Zoom Q&A Window
• No question is too small
• Questions will be answered in last 15 mins

6. SOLID Design Principles

7. Open Closed Principle
Class should be Open for extension but Closed for Modification.

8. Example
Create a Program to accept Circle and Square Object and return Sum of
their Area.

9. Example

12. Run Code

13. Change in Requirement
Add Support for Rectangle Also. What
would you do ?
Add one more If else? That would be
breaking Open Closed Principle. Class should
be closed to modification but open to
Extension.

14. Solution
Add Interface so that all Shape
should follow that interface, new
Class will become

15. Single Responsibility Principle
A class should have one and only one reason to change that means
only one job.

16. Example

19. Question
AreaCalculator class calculates area and returns result of sum of area
of all Shapes.
How to add functionality if we want to get area result as JSON or HTML
?

20. Answer
Incorrect

21. Explanation
Its breaking Single Responsibility Principle. AreaCalculator should only
change if formula related to Area changes

22. Liskov Substitution Principle
If class B is a child of class A, then A can be replaced by B, without
changing anything in a program. In other words, the LSP principle
states that you should not encounter unexpected results if child
(derived) classes are used instead of parent classes.

23. Interface Segregation Principle
This states that do not force a child class to depend on a method that is
not used for them. This principle suggests that you break interfaces
into smaller ones so that a client can only implement an interface that
is of interest.

24. Interface Segregation Principle

25. Dependency Inversion Principle
This states that modules should not depend on each other directly and
should depend via an interface (abstraction).

26. What are Design Patterns ?
Each Pattern describes
1. A problem which occurs again and again
2. A core of the Solution
3. Consequences of Solution

27. Design Patterns Does not
Provide Actual Implementation Details

28. Example - Roof Patterns in Construction

29. Who are Gang of Fours
Book written in 1994 consist of 23 Design
patterns by
1. Erich Gamma
2. Richard Helm
3. Ralph Johnson
4. John Vlissides

30. Gang of Four Patterns
Creational Patterns Structural Behavioral
1. Abstract Factory 6. Adapter 13. Chain of responsibility
2. Builder 7. Bridge 14. Command
3. Factory Method 8. Composite 15. Intercepter
4. Prototype 9. Decorator 16. Iterator
5. Singleton 10. Facade 17. Mediator
11. Fly Weight 18. Memento
12. Proxy 19. Observer
20. State
21. Strategy
22. Template Method
23. Visitor

31. Reference
• Apex Design Patterns
• SOLID Principle

32. Q&A

33. Next Episode 22
Design Pattern - 2

34. Thanks