introduction to the flow factory design pattern

Introduction to the Flow Factory Design Pattern Developers Track

Adam Purkiss, MondayCall Solutions, Principal Architect@apurkissadampurkiss.com

Learning the hard way…

ENTER COMMAND: GO NORTH■

Learning the hard way…

ENTER COMMAND: ■

Object-oriented design patterns▪ Program to an interface, not an implementation

▪ Strive for loosely-coupled designs▪ Encapsulate what varies▪ Remember the open-closed principle

Object-oriented design patterns

Requirements gathering

The problem

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Callout constraints

Deferring DML and email

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▪ 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()

The Flow Factory

Flow of the flow

Pass 1

Step 1▪Final processing

Pass 2 (DML)

Step 1▪Add self to list▪Process work▪Create next

Step 2▪…▪…▪…

Step 3▪…▪...▪…

Step 4▪...▪…▪Return null

Step 2▪…

Step 3▪…

Step 4▪…

Flow of the flow

Pass 1

Step 1finish()

Pass 2 (DML)

Step 1processStep()

Step 2processStep()

Step 3processStep()

Step 4processStep()

Step 2finish()

Step 3finish()

Step 4finish()

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

1) Next step / step name2) Process step / finish3) Create instance

FlowStep

1

3

2

▪ Create dynamic instance

FlowStep variation

1) Steps aggregate in parent list2) Flow-specific inputs in subclass

FlowState

2

1

1) Provide initial step & state2) Main loop (pass 1)3) Finish loop (pass 2)

FlowParent

3

1

2

1) Subclass FlowParent / processWork()2) Invoke flow

Invoking a flow example

2

1

Pass 1

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processStep()Nothing

processStep()Callout

processStep()Callout

processStep()Callout

Pass 2

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finish()Update Salesforce (DML)

finish()Save callout responseSend email

finish()Save callout responseSend email

finish()Save callout response

Demo

ResourcesGitHub:▪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-design-patterns-part2

Adam Purkiss

Principal Architect,@apurkiss