The document introduces the Flow Factory Design Pattern, emphasizing principles of object-oriented design such as programming to interfaces and ensuring loosely-coupled designs. It outlines the structure of flow execution via an inversion of control model with two passes for processing steps and finalizing actions. Additionally, it provides examples of logical interfaces and invokes flows, along with resources for further learning.

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