The Great Swift Migration

Migrating 30,000 lines of code from Objective-C to Swift

Transcript

1. The Great Swift Migration
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2. Self Intro
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3. — Name: Josh Kaplan
   — Company: GMO Pepabo
   — App: minne
   — Strengths: English
   — Hobbies: Collecting Xcode versions
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4. 30,000 lines of Obj-C
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5. Why?
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6. — Future proofing
   — Safety
   — Productivity with features like generics, etc
   — Security
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7. How?
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8. Modernize Objective-C
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9. @property (nonatomic, nonnull) NSArray *creators;
   @property (nonatomic, nonnull) MICartPayment *payment;
   @property (nonatomic, nonnull) MIAPIClient *client;
   @property (nonatomic, nullable) MICoupon *coupon;
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10. Check nullability in current Swift code
    let num: Int? = nil
    "\(num)" // String interpolation produces a debug description for an optional value
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11. Choosing which areas to migrate
    — First, modernize models
    — Then, ViewControllers and ViewModels/Presenters
    — Work on feature/module basis
    — Avoid converting code that is then used in obj-c
    — Cells and smaller views can wait
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12. Details
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13. Steps
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14. 1. Move properties in m file to header and add annotations
    2. Make Swift file and make extension
    3. Migrate non-lifecyle methods and commit for each method
    4. Make temporary method for lifecycle and IBAction method contents
    5. Migrate lifecycle methods and properties
    6. Update storyboard
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15. Points
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16. — Only minor refactoring
    — Writing tests first helps
    — Communicate with team to prevent conflicts
    — Things like major renaming should be in separate PRs to make review
    easier
    — Set goals and monitor progress with tools like tokei
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17. Bonus: Migrating to SwiftUI
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18. — Small components
    — Use Xcode Preview now
    — Fewer dependencies
    — Swift
    !
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