If you're an experienced Apex developer and have wondered if there?s a better way to manage multi-step logic that involves both DML and callouts to external systems, this session is for you. The Flow Factory is a stateful design pattern that provides structure for processing flowchart style business logic in Apex. This begins with flow-specific inputs and results in a chronological record of executed steps to iterate for final processing. It has roots in both the State pattern and the Factory Method and is particularly useful for managing more than one callout in a single execution context.

1. Introduction to the Flow Factory
Design Pattern
Developers Track
Adam Purkiss, MondayCall Solutions, Principal Architect
@apurkiss
adampurkiss.com

2. Learning the hard way…
ENTER COMMAND: GO NORTH
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3. Learning the hard way…
ENTER COMMAND:
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4. Object-oriented design patterns
▪ Program to an interface, not an implementation
▪
Strive for loosely-coupled designs
▪
Encapsulate what varies
▪
Remember the open-closed principle

5. Object-oriented design patterns

6. Requirements gathering

7. The problem
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8. The problem grew
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9. Callout constraints

10. Deferring DML and email
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11. The Flow Factory
▪ Flow-specific inputs
▪ Executed steps collection
▪ Steps create & return next steps
▪
Inversion of Control
▪ Two pass execution
▪
Pass 1: Step.processStep()
▪
Pass 2: Step.finish()

12. Flow of the flow
Pass 1
Step 1
Step 2
Step 3
Step 4
▪Add self to list
▪Process work
▪Create next
▪…
▪…
▪…
▪…
▪...
▪…
▪...
▪…
▪Return null
Step 1
Step 2
Step 3
Step 4
▪Final processing
▪…
▪…
▪…
Pass 2 (DML)

13. Flow of the flow
Pass 1
Step 1
Step 2
Step 3
Step 4
processStep()
processStep()
processStep()
processStep()
Step 1
Step 2
Step 3
Step 4
finish()
finish()
finish()
finish()
Pass 2 (DML)

14. Logical interfaces
▪ FlowStep (create / process / finish)
▪ FlowState (inputs / aggregate)
▪ FlowParent (process loop / finish loop)

15. FlowStep
1) Next step / step name
2) Process step / finish
3) Create instance
1
2
3

16. FlowStep variation
▪ Create dynamic instance

17. FlowState
1) Steps aggregate in parent list
2) Flow-specific inputs in subclass
1
2

18. FlowParent
1) Provide initial step & state
2) Main loop (pass 1)
3) Finish loop (pass 2)
1
2
3

19. Invoking a flow example
1) Subclass FlowParent / processWork()
2) Invoke flow
1
2

20. Pass 1
processStep()
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processStep()
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21. Pass 2
finish()
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finish()
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finish()
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22. Demo

23. Resources
GitHub:
▪https://github.com/apurkiss/course-complete
Developerforce Wiki:
▪http://wiki.developerforce.com/page/The_Flow_Factory_Design_Pattern
Pluralsight: Force.com Design Patterns - Part 2
▪http://pluralsight.com/training/Courses/TableOfContents/forcedotcom-designpatterns-part2

24. Adam Purkiss
Principal Architect,
@apurkiss