iOSDevUK 2015: Clean Code through Dependency Injection

This is a 5 minute fast-talk we gave at iOSDevUK 2015.

Transcript

1. Clean Code through 

   Dependency Injection
   

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2. Your host
   Mike Seghers
   Developer/Architect
   mike@appfoundry.be
   @mikeseghers
   

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3. Creating apps: a recent history
   

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5. 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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6. 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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8. 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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9. 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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10. Current
    

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11. 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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12. 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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13. How many app factories does one
    need?
    

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14. 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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15. 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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16. 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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17. 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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18. Dependency Injection
    

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19. Helps with reusable code
    

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20. Dependency Injection
    

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21. Helps with loose coupling
    

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22. Dependency Injection
    

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23. Helps with (unit) tests
    

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24. Dependency Injection
    

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25. Helps keep your code clean
    

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26. Questions?
    Come talk to me!
    Mike Seghers
    Developer/Architect
    mike@appfoundry.be
    @mikeseghers
    https://github.com/appfoundry/Reliant
    

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