So long, Flow Controller

Presented at CocoaHeads Montreal on September 26th, 2019.

Transcript

1. So long, Flow Controller
   Olivier Collet. CocoaHeads Montreal. 26.09.2019
   

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2. The Story
   

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3. December 2012

   Seb Morel presents at CocoaHeads Montreal:

   “How to Avoid the Flying Spaghetti Code Monster!”
   

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4. Flow Manager
   MVC
   Intent
   1. Get Model
   2. Setup Flow
   Dependent
   Elements
   3. Presents
   MVC
   Intent
   1. Get Model
   2. Setup Flow
   Dependent
   Elements
   3. Presents
   MVC
   Intent
   1. Get Model
   2. Setup Flow
   Dependent
   Elements
   3. Presents
   MVC
   Intent
   1. Get Model
   2. Setup Flow
   Dependent
   Elements
   3. Presents
   MVC
   Intent
   1. Get Model
   2. Setup Flow
   Dependent
   Elements
   3. Presents
   

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5. January 2014

   CocoaHeads Paris:

   “Flow Controller”
   

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6. February 2014

   Blog post:

   “Give Your App a Brain With a Flow Controller”
   

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7. January 2015

   Soroush Khanlou writes a blog post:

   “The Coordinator”
   

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8. February 2016

   CocoaHeads Montreal:

   “Flow Controller - Revisited”
   

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9. Flow Controller
   1. Keep the application’s state
   2. Manage the logic between view controllers
   3. Orchestrate the view controllers
   4. Prevent view controller dependencies
   5. Handle a portion of the application
   

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10. Flow Controller
    

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11. Flow Controller
    ☠
    DEAD
    

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12. Best code is no code.
    

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13. Inherits from UIResponder
    with a reference to a root UIViewController
    Inherits from UIViewController
    UINavigationController, UITabBarController, or custom container view controller
    
    

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14. View controllers report via delegate
    with lots of delegate protocols in a complex view controller hierarchy
    View controllers report via the responder chain
    low key introducing the Event and EventHandler protocols
    
    

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15. Event + EventHandler
    

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16. Event

    protocol
    • Similar to Error

    Can be used as an enum with associated values 

    or as a struct with properties
    • Passed along the responder chain

    

    protocol Event {
    }
    

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17. EventHandler

    protocol
    • Implement to receive Events
    • Specifies the event that can keep being propagated

    down the responder chain or no event to propagate
    protocol EventHandler: AnyObject {
    func handleEvent(_ event: Event) -> Event?
    }
    

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18. UIResponder

    extension
    • func postEvent(_ event: Event)

    propagates the event up the responder chain
    • var eventHandler: EventHandler?

    can be used to hook an object that is not part of the responder chain

    

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19. Annie Spratt
    

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20. References
    • https://github.com/smorel/CocoaHeads-Avoiding-Spaghetti-Code/
    blob/master/cocoaheads%20-
    %20How%20to%20avoid%20the%20spaghetti%20code%20Monster.pd
    f
    • https://speakerdeck.com/ocollet/flow-controller-give-your-app-a-brain
    • https://ocollet.com/2014/02/06/flow-controller/
    • http://khanlou.com/2015/01/the-coordinator/
    • https://speakerdeck.com/ocollet/flow-controller-revisited
    • https://gist.github.com/ocollet/719216edad74a5135470cf508bf50277
    

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21. Olivier Collet

    @ocollet
    ✌
    

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