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Clean Code through 
 Dependency Injection

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Your host Mike Seghers Developer/Architect [email protected] @mikeseghers

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Creating apps: a recent history

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2012

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Coding Example Acceptable in 2012 struct SkeumorphicDesigner { func createDesign(requirements: Requirements) -> Design { //Draws some boxes with stitches, applies colors //returns Design } } struct ObjectiveCDeveloper { func createApp(requirements: Requirements, design: Design) -> App { //Does some code between [], applies the design using //InterfaceBuilder, returns App }

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Coding Example Acceptable in 2012 class AppFactory2012 { private let developer:ObjectiveCDeveloper private let designer:SkeumorphicDesigner init() { developer = ObjectiveCDeveloper() designer = SkeumorphicDesigner() } public func createApp(requirements:Requirements) -> App { let design = designer.createDesign(requirements) return developer.createApp(requirements, design: design) } } … let appFactory = AppFactory2012() let app = appFactory.createApp(requirements)

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2013

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Coding Example Acceptable in 2013 struct FlatDesigner { func createDesign(requirements: Requirements) -> Design { //Draws some flat boxes, applies less color, returns Design } } struct ObjectiveCDeveloper { … }

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Coding Example Acceptable in 2013 class AppFactory2013 { private let developer:ObjectiveCDeveloper private let designer:FlatDesigner init() { developer = ObjectiveCDeveloper() designer = FlatDesigner() } public func createApp(requirements:Requirements) -> App { let design = designer.createDesign(requirements) return developer.createApp(requirements, design: design) } } … let appFactory = AppFactory2013() let app = appFactory.createApp(requirements)

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Current

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Coding Example Acceptable in now struct SwiftDeveloper { func createApp(requirements: Requirements, design: Design) -> App { //Does some code without semi-colons, applies the //design using StoryBoards, returns App } struct FlatDesigner { … }

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Coding Example Acceptable in now class AppFactory2014 { private let developer:SwiftDeveloper private let designer:FlatDesigner init() { developer = SwiftDeveloper() designer = FlatDesigner() } public func createApp(requirements:Requirements) -> App { let design = designer.createDesign(requirements) return developer.createApp(requirements, design: design) } } … let appFactory = AppFactory2014() let app = appFactory.createApp(requirements)

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How many app factories does one need?

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Coding Example Acceptable all the time protocol Designer { func createDesign(requirements: Requirements) -> Design } protocol Developer { func createApp(requirements: Requirements, design: Design) -> App } extension SkeumorphicDesigner : Designer {} extension FlatDesigner : Designer {} extension ObjectiveCDeveloper : Developer {} extension SwiftDeveloper : Developer {}

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Coding Example Acceptable all the time class AppFoundry { private let developer:Developer private let designer:Designer init(developer: Developer, designer: Designer) { self.developer = developer self.designer = designer } func createApp(requirements:Requirements) -> App { let design = designer.createDesign(requirements) return developer.createApp(requirements, design: design) } }

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Coding Example Acceptable all the time let developer = ObjectiveCDeveloper() let designer = SkeumorphicDesigner() let oldSchoolFoundry = AppFoundry(developer: developer, designer: designer) oldSchoolFoundry.createApp(requirements)

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Coding Example Acceptable all the time let developer = ObjectiveCDeveloper() let designer = FlatDesigner() let playingItSaveFoundry = AppFoundry(developer: developer, designer: designer) playingItSaveFoundry.createApp(requirements)

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Dependency Injection

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Helps with reusable code

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Dependency Injection

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Helps with loose coupling

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Dependency Injection

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Helps with (unit) tests

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Dependency Injection

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Helps keep your code clean

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Questions? Come talk to me! Mike Seghers Developer/Architect [email protected] @mikeseghers https://github.com/appfoundry/Reliant