Getting Swifty in an Objective-C World
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The document discusses the transition from Objective-C to Swift within a mobile engineering team, highlighting the challenges of interoperability and the decision-making process for adoption. It emphasizes the importance of leveraging Swift's modern features while managing existing Objective-C code, using 'shims' to bridge both languages effectively. The outcome has led to a notable shift, with many apps now incorporating significant Swift components and improvements in compatibility with Objective-C.
![Exhibit A
enum LocalizedStrings: String {
case wishlist_home_button_title
case customer_service_phone_number
case credit_card_scan_flash_on
case credit_card_scan_flash_off
}
func localized(string string: LocalizedStrings) -> String {
return NSLocalizedString(string.rawValue, comment: string.rawValue)
}
class CompatLocalization: NSObject {
@objc static func wishlistHomeButtonTitle() -> String {
return localized(string: .wishlist_home_button_title)
}
@objc static func customerServicePhoneNumber() -> String {
return localized(string: .customer_service_phone_number)
}
@objc static func creditCardScanOn() -> String {
return localized(string: .credit_card_scan_flash_on)
}
@objc static func creditCardScanOff() -> String {
return localized(string: .credit_card_scan_flash_off)
}
}
...
[CompatLocalization wishlistHomeButtonTitle]
[CompatLocalization customerServicePhoneNumber]
[CompatLocalization creditCardScanOn]
[CompatLocalization creditCardScanOff]
String backed enums and global functions oh my
Enum backed
by string
Global Function
Obj-C Bridgeable class
w/ static functions
Obj-C interacting w/ static
compat functions](https://image.slidesharecdn.com/gettinswifty-160504172411/85/Getting-Swifty-in-an-Objective-C-World-7-320.jpg)
![Exhibit B
protocol AnalyticsCollection {
func sendEvent()
}
enum AnalyticsEvent {
enum Global: AnalyticsCollection {
case AppLaunchedFromSpotlight(activityURL: String)
case AppLaunchedFromUniversalLink(activityURL: String
func sendEvent() { ... }
}
}
...
class ANTAnalytics : NSObject, UCOAnalyticsProvider { ... }
extension ANTAnalytics {
func logAppLaunchedFromSpotlight(activityURL: String) {
AnalyticsEvent.Global.AppLaunchedFromSpotlight(activityURL: activityURL).sendEvent()
}
func logAppLaunchedFromUniversalLink(activityURL: String) {
AnalyticsEvent.Global.AppLaunchedFromUniversalLink(activityURL: activityURL).sendEvent()
}
}
...
[[ANTAnalytics sharedInstance] logAppLaunchedFromUniversalLink:activityURL];
[[ANTAnalytics sharedInstance] logAppLaunchedFromSpotlight:activityURL];
Nested types, enums that conform to a protocol & have functions
Enum without backing value,
conforming to protocol,
with function
Extension on Obj-C
bridgeable type
Obj-C interacting w/ compat
functions](https://image.slidesharecdn.com/gettinswifty-160504172411/85/Getting-Swifty-in-an-Objective-C-World-8-320.jpg)
Getting Swifty in an Objective-C World
- 1. Getting Swifty in an Objective-C World ENGINEERING Jason Grandelli // Mobile Engineering Manager @ URBN, inc
- 2. The Situation • 9 engineers, ~8 Obj-C apps, ~6 Obj-C shared frameworks • 100’s of thousands of lines of Obj-C • Swift matures with 2.0 • New features, production timelines • Decision time - pull the trigger on Swift or fall behind! • Our path to Swifty was paved with good intentions
- 3. Swift vs Objective-C • Obj-C > 30 yrs old, Swift 2 years old • Dynamic vs Static • Superset of C vs Best bits of everything • Support for modern features such as tuples, optionals, simplified file structure, access modifiers, generics, functional bits • Mostly full interoperability, kind of #codeFight #holyWar #changeIsHard
- 4. Interop • Swift.h & Bridging-Header.h • @objc to explicitly declare availability • Add support for nullability & generics to make your Obj-C more predictable #itJustWorks NS_ASSUME_NONNULL_BEGIN … NS_ASSUME_NONNULL_END @property (nonatomic, copy) NSArray<NSString *> * _Nullable items; @property (nonatomic, copy) NSString * _Nonnull title; - (NSURL * _Nullable)urlFromString:(NSString * _Nonnull)name;
- 5. Interop is Hard All of the coolest features don’t bridge 😢 • Generics • Tuples • Enums defined in Swift • Structs defined in Swift • Top-level functions defined in Swift • Global variables defined in Swift • Typealiases defined in Swift • Swift-style variadics • Nested types • Objective-C can’t inherit from Swift types Or screw it lets burn it all to the ground and start over.
- 6. Shim All The Things • Dope new features or Legacy Support? False Dichotomy. • Priority is to learn & use Swift as the creators intended • Writing Objective-C styled Swift is a waste of time • New Swift code should be free of debt • No time to start over with 100% Swift • Enter shims to keep us Swifty and appease our Obj-C captors
- 7. Exhibit A enum LocalizedStrings: String { case wishlist_home_button_title case customer_service_phone_number case credit_card_scan_flash_on case credit_card_scan_flash_off } func localized(string string: LocalizedStrings) -> String { return NSLocalizedString(string.rawValue, comment: string.rawValue) } class CompatLocalization: NSObject { @objc static func wishlistHomeButtonTitle() -> String { return localized(string: .wishlist_home_button_title) } @objc static func customerServicePhoneNumber() -> String { return localized(string: .customer_service_phone_number) } @objc static func creditCardScanOn() -> String { return localized(string: .credit_card_scan_flash_on) } @objc static func creditCardScanOff() -> String { return localized(string: .credit_card_scan_flash_off) } } ... [CompatLocalization wishlistHomeButtonTitle] [CompatLocalization customerServicePhoneNumber] [CompatLocalization creditCardScanOn] [CompatLocalization creditCardScanOff] String backed enums and global functions oh my Enum backed by string Global Function Obj-C Bridgeable class w/ static functions Obj-C interacting w/ static compat functions
- 8. Exhibit B protocol AnalyticsCollection { func sendEvent() } enum AnalyticsEvent { enum Global: AnalyticsCollection { case AppLaunchedFromSpotlight(activityURL: String) case AppLaunchedFromUniversalLink(activityURL: String func sendEvent() { ... } } } ... class ANTAnalytics : NSObject, UCOAnalyticsProvider { ... } extension ANTAnalytics { func logAppLaunchedFromSpotlight(activityURL: String) { AnalyticsEvent.Global.AppLaunchedFromSpotlight(activityURL: activityURL).sendEvent() } func logAppLaunchedFromUniversalLink(activityURL: String) { AnalyticsEvent.Global.AppLaunchedFromUniversalLink(activityURL: activityURL).sendEvent() } } ... [[ANTAnalytics sharedInstance] logAppLaunchedFromUniversalLink:activityURL]; [[ANTAnalytics sharedInstance] logAppLaunchedFromSpotlight:activityURL]; Nested types, enums that conform to a protocol & have functions Enum without backing value, conforming to protocol, with function Extension on Obj-C bridgeable type Obj-C interacting w/ compat functions
- 9. Where are they now? • Every app now contains between 5-20+% • 1 app 100% swift • New shared frameworks all in swift • All Objective-C updated to better work with Swift • Slowly but surely gettin rid of the Objective-C We got Swifty!