A Busy Developer’s Guide to native iOS apps Android vs. iOS. It’s a frequent discussion between developers on which is better, faster, easier to develop with. In general, developers pick one platform to focus on—however, it’s imperative for strong developers to have an understanding of both platforms and be able to see a problem from both perspectives. The platforms are unique but also evolve together, matching features. As a Senior Software Engineer at The New York Times, I develop both native Android and iOS core libraries for our apps. In this presentation, we will discuss some of the similarities and differences between Android & iOS and give developers a better understanding of native iOS from an Android perspective. In this presentation, you will learn about: Design Element differences Swift vs. Kotlin iOS app setup & structure (Xcode vs. Gradle) iOS app lifecycles MVVM Jetpack Compose vs. Swift UI By the end of this talk, you will be able to better understand Swift code, bring both platform perspectives to product and architecture conversations, and have more confidence contributing to iOS apps and libraries. https://chicagoroboto.com/session/understanding-native-ios-from-an-android-perspective/

1. Understanding iOS from an
Android perspective
A Busy Developer’s Guide to native iOS apps
Lauren Yew
Sept 28th, 2021
The New York Times
?

2. Let’s start
with a caveat

3. PetAdopt Sample App
iOS Android

4. Topics
1. Design Differences
2. Swift vs. Kotlin
3. App Setup & Structure
4. App Lifecycles & Architecture Patterns
5. SwiftUI vs. Jetpack Compose
?

5. Topics
1. Design Differences
2. Swift vs. Kotlin
3. App Setup & Structure
4. App Lifecycles & Architecture Patterns
5. Swift UI vs. Jetpack Compose

6. Design Differences
iOS Android
Apple Human Interface
Guidelines
Material Design

7. Design Differences
iOS Android
Home Button Only
Home Button + Back Button
(*sometimes represented by gestures
depending on navigation settings)

8. Back Buttons
iOS Android
Back Button
always present
No Back Button

9. iOS
Selection Options
Android

10. iOS
Selection Options
Android
Switch per option

11. iOS
Errors
Android

12. Topics
1. Design Differences
2. Swift vs. Kotlin
3. App Setup & Structure
4. App Lifecycles & Architecture Patterns
5. Swift UI vs. Jetpack Compose

13. Swift
Declaring Variables
Kotlin

14. Swift
Declaring Variables
Kotlin

15. Swift
Optionals
Kotlin

16. Swift
Optionals
Kotlin
Optional Chaining Safe Call

17. Swift
Optionals
Kotlin
Nil Coalescing Elvis Operator

18. Swift
Optionals
Kotlin

19. Swift
Optionals
Kotlin

20. Swift
Optionals
Kotlin
Force Unwrap
Required each
time.

21. Guard + Let
Pattern of
Early Exit
Swift

22. Guard + Let
Swift

23. Swift
Functions
Kotlin

24. Swift
Functions
Kotlin

25. Swift
Functions
Kotlin
Parameter
names required
unless have _

26. Swift
Protocols
Kotlin

27. Swift
Protocols
Kotlin

28. Swift
Protocols
Kotlin

29. Struct Class
Swift
Structs vs. Classes

30. Swift
Structs vs. Classes

31. Struct Class
Swift
Structs vs. Classes

32. Swift Kotlin
Class Inheritance
Same
Module
Same /
Different
Module

33. Class Inheritance
Swift Kotlin
Different
Module
Same /
Different
Module

34. • All protocols, classes, and structs
are extendable.
• Expect extensions on classes to
help modularize the code (within
the same class or in other
classes)
• Search by class name to find
where it has been extended
Swift
Extensions

35. Topics
1. Design Differences
2. Swift vs. Kotlin
3. App Setup & Structure
4. App Lifecycles & Architecture Patterns
5. Swift UI vs. Jetpack Compose
...

36. Xcode Basics

37. Opening a workspace
Project
Workspace
*always use this option if it’s
available

38. Workspace
What documents / projects do I contain?
At a high level
Project Project
Represents
app/library/framework.
What are the source
documents, file structure, and
basic project wide settings?
Project
Target
Target
Target
How to build / run each
app / library?
Target
Target

39. Projects and Targets in Xcode

40. Projects and Targets in Xcode

41. Projects and Targets in Xcode

42. Projects and Targets in Xcode

43. Projects and Targets in Xcode

44. Projects and Targets in Xcode

45. iOS App Structure

46. Terminology
• Bundle (represents executable app /
framework)
• Framework = library module
• Application Bundle: Info.plist, executable,
& resource files

47. Info.plist
• Information Property List (similar
to AndroidManifest + parts of
build.gradle)
• XML file encoded w/ UTF-8

48. Info.plist

49. Working w/ Dependencies (Cocoapods)
Another option: SPM (Swift
Package Manager)

50. Working w/ Dependencies
Cocoapods (iOS) Gradle (Android)

51. Working w/ Dependencies
Cocoapods (iOS) Gradle (Android)

52. Working w/ Dependencies
Cocoapods (iOS) Gradle (Android)

53. Working w/ Dependencies (Cocoapods)
Central Repository
(trunk)

54. How does Cocoapods Work?

55. Popular iOS Third Party Libraries
• Alamofire / AFNetworking (HTTP calls)
• Lottie (Image Rendering)
• RxSwift (RxJava for Swift) or just use Combine
• YapDatabase (Sqlite Database – similar to Room)
• Resolver (Dependency Injection – similar to Hilt)

56. Topics
1. Design Differences
2. Swift vs. Kotlin
3. App Setup & Structure
4. App Lifecycles & Architecture Patterns
5. Swift UI vs. Jetpack Compose
......

57. Main iOS App Lifecycles
Not Running
App is in foreground
Inactive
Active
App is in background
Background
Suspended

58. Handling iOS App Lifecycles
callbacks for lifecycle
callbacks windows / UI lifecycles
SwiftUI Apps
This is an example of a SwiftUI app entry point w/ @main
App can be configured to use AppDelegate
Scene replaces SceneDelegate
UIViewController / Non-Swift UI

59. Main iOS App Lifecycles
Not Running
Finished launching,
next step to come into
foreground

60. Main iOS App Lifecycles
Not Running
App is in foreground
Inactive

61. Main iOS App Lifecycles
App is in foreground
Inactive
Active

62. Main iOS App Lifecycles
App is in foreground
Inactive
Active

63. Architecture Patterns

64. Common Architecture Patterns
• MVC (Model View Controller) aka. Massive View Controller
• MVP (Model View Presenter)
• MVVM (Model View ViewModel)
• VIPER (View, Interactor, Presenter, Entity, & Router)

65. MVVM on iOS
• No viewModel is built in with iOS
• POJO w/ properties and/or
functions for view to react on or
update
• Up to devs to determine how
much business logic in
viewModel

66. Topics
1. Design Differences
2. Swift vs. Kotlin
3. App Setup & Structure
4. App Lifecycles & Architecture Patterns
5. Swift UI vs. Jetpack Compose
!

67. Basic Structure
SwiftUI Jetpack Compose

68. Columns & Rows
SwiftUI Jetpack Compose

69. Columns & Rows
SwiftUI Jetpack Compose

70. Modifiers
SwiftUI Jetpack Compose

71. Getting Data to the UI
SwiftUI Jetpack Compose

72. Getting Data to the UI
SwiftUI Jetpack Compose

73. Getting Data to the UI
SwiftUI Jetpack Compose

74. Thank You
@YewLauren

75. Appendix

76. The New York Times is Hiring!
NYT Android & iOS Apps (News, Cooking, Games)
Come work with us.
https://www.nytco.com/careers/

77. Resources
• https://learnui.design/blog/ios-vs-android-app-ui-design-complete-guide.html
• https://uxdesign.cc/ios-vs-android-design-630340a73ee6
• https://willowtreeapps.com/ideas/swift-and-kotlin-the-subtle-differences
• https://developer.apple.com/library/archive/documentation/CoreFoundation/Conceptual/CFBundl
es/BundleTypes/BundleTypes.html#//apple_ref/doc/uid/10000123i-CH101-SW1
• https://developer.apple.com/videos/play/wwdc2018/415/
• https://manasaprema04.medium.com/application-life-cycle-in-ios-f7365d8c1636
• https://www.vadimbulavin.com/swiftui-view-lifecycle/
• https://developer.apple.com/documentation/uikit/app_and_environment/scenes/preparing_your_
ui_to_run_in_the_background
• https://learnappmaking.com/swiftui-app-lifecycle-how-to/
• https://www.vadimbulavin.com/swiftui-view-lifecycle/
• https://kotlinlang.org/docs/keyword-reference.html#special-identifiers
• https://medium.com/swlh/bye-bye-appdelegate-swiftui-app-life-cycle-58dde4a42d0f
• PetAdopt Sample App: https://github.com/laurenyew/PetAdoptSampleApp/tree/develop/ios

78. Back Buttons
iOS Android
Back Button w/
Title

79. Back Buttons
iOS Android
Hit back button

80. iOS
Main Action Button
Android
+ on right
Floating Action
Button

81. iOS
Primary Navigation
Android
Tab Bar
Top nav buttons

82. Swift
Structs vs. Classes
Struct Class

83. iOS
• Lists are Tables
• SwiftUI à List {…}
• Lists are RecyclerViews +
Adapters / ListViews
• JetpackCompose à Lists are
LazyColumns
Lists
Android

84. ARC vs Garbage Collection
• ARC = automatic reference counting
• Improved performance (any numbers?)
• How it works? Counts number of references on a class then if number
is 0, removes that bit of data, unlike Garbage collection that waits till a
moment in time then cleans up things that don’t have references
• Requirements for weak self in closure (similar to do not pass context
references) ß needs code example

85. Loading up an Application
• .xcodeproj file (list of files / objects for
xcode to load) – grouped by type
• Xcode builds application w/ configuration on
`target` with rules to build bundle from
Info.plist + source files
• Compile task: takes source code (.h, .m,
.swift) and makes into object files (.o)
• Link task: links object files to make
executable library output file (.app)

86. SwiftUI Lifecycles
Appearing
Layout
Commit

87. SwiftUI Lifecycles
Updating
Diff
Update Body and re-
render required UI

88. SwiftUI Lifecycles
Disappearing
On Disappear

89. iOS
Modularizing
Android

90. Extra Modularizing

91. How does Cocoapods Work?

92. How does Cocoapods Work?

93. On Background
• Save User State / Data
• Suspend dispatch / operation queues
• Don’t start any new tasks
• App will take snapshot image of current state
to show when app is starting back up
(*Android also does this)
App Manager