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The Great Swift Migration
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Self Intro
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— Name: Josh Kaplan
— Company: GMO Pepabo
— App: minne
— Strengths: English
— Hobbies: Collecting Xcode versions
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30,000 lines of Obj-C
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Why?
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— Future proofing
— Safety
— Productivity with features like generics, etc
— Security
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How?
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Modernize Objective-C
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@property (nonatomic, nonnull) NSArray *creators;
@property (nonatomic, nonnull) MICartPayment *payment;
@property (nonatomic, nonnull) MIAPIClient *client;
@property (nonatomic, nullable) MICoupon *coupon;
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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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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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Details
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Steps
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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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Points
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— 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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Bonus: Migrating to SwiftUI
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— Small components
— Use Xcode Preview now
— Fewer dependencies
— Swift
!
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