Swift, Meet Storyboard

Swift London (October 19, 2015) talk. Talk about Natalie - Storyboard Code Generator presenting my approach to the "problem" of Storyboards and Swift.

Transcript

1. Swift London, 19 Oct 2015
   Swift, meet Storyboard
   

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2. Welcome
   Marcin Krzyżanowski
   blog.krzyzanowskim.com
   @krzyzanowskim
   

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3. Storyboards
   “A storyboard is a visual representation of the user
   interface of an iOS application, showing screens of
   content and the connections between those screens”
   

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4. Storyboard
   » scenes
   » segues between scenes
   » controls used to trigger
   the segues
   

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5. Storyboard
   » graphical representation of
   a interface
   » visual editor: Interface
   Builder
   » not a code
   » structured XML document
   (compiled to nibs)
   » loaded in runtime
   

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8. Storyboard,
   meet Swift
   

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9. As it is
   » string based identifiers
   » UIViewController
   

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10. Problems
    » error prone refactoring
    » traversing view controllers/storyboards
    » massive Storyboard (not necessarily)
    » more
    

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11. Strings everywhere
    

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12. Strings everywhere
    let storyboard = UIStoryboard(name: "Main", bundle: nil)
    let vc = storyboard.instantiateViewControllerWithIdentifier("MainViewController")
    

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13. Strings everywhere - refactoring
    week later
    storyboard.instantiateViewControllerWithIdentifier("ZweiMainViewController")
    *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason:
    'Storyboard () doesn't contain a view controller with identifier 'ZweiMainViewController''
    *** First throw call stack: (
    0 CoreFoundation 0x0000000104f88f65 __exceptionPreprocess + 165
    1 libobjc.A.dylib 0x0000000106c1adeb objc_exception_throw + 48
    2 UIKit 0x0000000105e855d4 -[UIStoryboard instantiateInitialViewController] + 0
    )
    

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14. Strings everywhere - Refactoring
    func performSegueWithIdentifier(identifier: String, sender: AnyObject?)
    *** Terminating app due to uncaught exception 'NSInvalidArgumentException',
    reason: 'Receiver ()
    has no segue with identifier 'GoToMainView''
    *** First throw call stack: (
    0 CoreFoundation 0x000000010634df65 __exceptionPreprocess + 165
    1 libobjc.A.dylib 0x0000000107fdfdeb objc_exception_throw + 48
    )
    

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15. UIViewController everywhere
    func instantiateInitialViewController() -> UIViewController?
    func instantiateViewControllerWithIdentifier(identifier: String) -> UIViewController
    returning type? I don't know.
    

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16. as!
    instantiateInitialViewController() as! OtherViewController
    Could not cast value of type
    'MainViewController'
    to 'OtherViewController'.
    

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17. Swift,
    meet Storyboard
    

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19. compile time safety
    Strong Type System
    

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20. Wouldn't be nice go from this:
    storyboard.instantiateViewControllerWithIdentifier("MainViewController")
    to this
    storyboard.instantiateViewController(MainViewController)
    and feel safe
    

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21. Parse and conquer
    Layer
    - .storyboard
    Layer
    - source code
    

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22. Parse and conquer
    Layer
    - .storyboard
    Layer
    - generator
    Layer
    - source code
    

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23. Storyboard, Swift,
    meet Natalie
    

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25. Natalie
    Storyboard Code Generator
    

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26. Natalie
    » Open Source (github: krzyzanowskim/Natalie)
    » CLI tool
    » Swift script
    » #!/usr/bin/env xcrun -sdk macosx swift
    » Homebrew
    » $ brew install natalie
    

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27. Storyboards.swift
    

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28. Natalie
    Integrates with Xcode
    Build Phases
    

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29. View Controllers
    struct Storyboards {
    struct Main {
    static func instantiateViewController(type: T.Type) -> T?
    static func instantiateMainViewController() -> MainViewController
    static func instantiateSecondViewController() -> ScreenTwoViewController
    }
    struct Settings {
    ...
    }
    }
    Instantiate view controllers:
    let vc = Storyboards.Main.instantiateViewConrtoller(MainViewConrtoller)
    let vc = Storyboards.Main.instantiateMainViewController()
    let vc = Storyboards.Main.instantiateSecondViewController()
    Notice: "vc" has right type:
    

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30. Segues
    extension MainViewController {
    enum Segue: String, CustomStringConvertible, SegueProtocol {
    case ScreenOneSegueButton = "Screen One Segue Button"
    var kind: SegueKind? // .Push, .Modal, etc...
    var identifier: String?
    var destination: UIViewController.Type?
    }
    }
    

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31. Segues
    var destination: UIViewController.Type? {
    switch (self) {
    case ScreenOneSegueButton:
    return ScreenOneViewController.self
    case ScreenOneSegue:
    return ScreenOneViewController.self
    }
    }
    in theory:
    MainViewController.Segue.ScreenOneSegue.destination!.init(nibName: nil, bundle: nil)
    

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32. Perform Segues
    vc.performSegue(MainViewController.Segue.ScreenOneSegue)
    override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
    if segue == MainViewController.Segue.ScreenOneSegue {
    // handle segue
    }
    }
    

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33. More
    » UITableView reusable cells
    » UICollectionView reusable cells
    » Compare segues (segue1 == segue2)
    

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34. Recap
    » Storyboard is external to the code
    » Strings are error prone
    » Swift is Strongly Typed
    » Middleman generator can create bridge between two
    worlds
    » Natalie
    

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36. Thank you
    Marcin Krzyżanowski
    blog.krzyzanowskim.com
    @krzyzanowskim
    

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