Scaling Your iOS Codebase

Many companies and independent developers face an issue as their apps and teams grow. It usually starts as a single application, with all the sources and resources as a single bundle packaging it all. Add to that equation app extensions, the need to have more apps sharing the same code, multiple git repositories, multiple developers, a growing Xcode project file, longer build times... Now you have the recipe for the perfect iOS developer headache!

This talk discusses 5 common challenges many companies and developers face when scaling their codebase and team, as well as our approach at Houzz:

1. Xcode Project Management
2. Build Times
3. Reusing Code
4. Modularization
5. Maintenance & Automation

Some useful, related, and discussed links:

Xcode Project Management:
Tuist, XcodeGen, Xcake, Bazel and Buck.

Build Times:
XCLogParser by Spotify

Modularization:
- Swift Rocks: Reducing iOS Build Times by Using Interface Targets by Bruno Rocha.
- RouterService

Maintenance & Automation:
- Swift Argument Parser
- Prism by Gett Engineering
- SwiftGen
- Danger

Transcript

1. Scaling Your iOS Codebase Challenges and approaches from our experience at Houzz
2. About me Natan Rolnik iOS Infra Engineer • Started developing on iOS 3 • Server-Side Swift Author @ RayWenderlich.com • Joined Houzz in 2019 • Always loved working on UI, animations • Joined the new Infra team at Houzz around 1 year ago
3. iOS @ Houzz: an overview
4. iOS at Houzz How our products grew in a decade 2010 iPad App 2020 Houzz Pro 2017 AR iPhone App 2013 iOS 7 2014 App Extensions 2016 tvOS
5. +15 Internal Frameworks Swift + ObjC iOS at Houzz 2 Apps 6 App Extensions
6. iOS at Houzz In a nutshell
7. Sounds familiar?
8. Agenda 5 Challenges Xcode Project Management Maintenance & Automation Reusing Code Modularization Build Times !
9. Xcode Project Management Challenge #1
16. Xcode Project Management The Problem Develop a branch and merge .pbxproj Merge Conflict Try to Solve Conflict No conflicts Merge successful, but wasted time Merge went wrong (missing sources, resources or settings)
17. Xcode Project Management The Problem ! Hard to read & maintain " Doesn’t reflect file system # Settings & Linking error prone $ Larger teams %& Multiple branches
18. Xcode Project Management
19. Xcode Project Management The Solution Describe your project Sources, Resources, Targets, Settings…
20. Xcode Project Management The Solution Describe your project Sources, Resources, Targets, Settings…
21. Xcode Project Management The Solution
22. • How to describe your project? • Allows a gradual transition? • How hard is it for a small-medium sized iOS team to start using? • Allows sharing settings/standards between projects? • Replaces Xcode build system? • Allows caching? Xcode Project Management Alternatives XcodeGen Xcake Tuist Bazel/Buck
23. Xcode Project Management Tuist • Makes maintaining, interacting, and scaling Xcode projects enjoyable • Any developer in the team is able to do “infra” tasks • By being aware of the dependency tree, it owns the complexity • “On demand” workspaces/projects • Cache
24. Xcode Project Management Tuist
25. Long Build Times Challenge #2
26. Long Build Times https://xkcd.com/303/
27. Long Build Times The Problem !" Code Changes ! Clear Derived Data git Git Operations
28. Long Build Times The Reasons • Massive files • Mixed Obj-C and Swift code • Long functions • Long expressions & type inference • Build phases
29. Long Build Times Solutions
30. Long Build Times Solutions
31. Long Build Times Solutions
32. Long Build Times Solutions
33. • Show slowly compiling functions and expressions • Add to Other Swift Flags (in Debug): Long Build Times Solutions -Xfrontend -warn-long-function-bodies=100 -Xfrontend -warn-long-expression-type-checking=100
34. • Access Control: private, fileprivate and final wherever possible • Avoid defining many types in the same file • Make sure to use appropriate Build Settings: • Build Active Architecture - set to Yes for Debug • Debug Information Format - set not to use dSYMs in Debug (DWARF only) • Enable Whole Module Optimization • New Build Sytem (Xcode 9) Long Build Times Solutions
35. • Delete unused code • Reevaluate dependencies constantly • Show build times in Xcode: Long Build Times Solutions $ defaults write com.apple.dt.Xcode ShowBuildOperationDuration -bool YES
36. • If possible and makes sense, move dependencies to their pre-compiled versions • Modularize your codebase correctly • Check if caching modules is a possibility Long Build Times Solutions
37. Reusing Code Challenge #3
38. Reusing Code The Problem Target Membership My MVP App ✓ Model.swift CoreDataStack.swift Networking.swift
39. Reusing Code The Problem My App Share Extension My App Widget My App Notification Extension Target Membership My MVP App ✓ Model.swift CoreDataStack.swift Networking.swift
40. Reusing Code The Problem My App Share Extension My App Widget My App Notification Extension Target Membership My MVP App ✓ ✓ ✓ ✓ Model.swift CoreDataStack.swift Networking.swift
41. Reusing Code The Problem My App Share Extension My App Widget My App Notification Extension Target Membership My MVP App ✓ ✓ ✓ ✓ Model.swift CoreDataStack.swift Networking.swift
42. Reusing Code The Alternatives 1. Package Managers: Swift Package Manager, CocoaPods, Carthage 2. Manual Integration: Workspace with multiple Xcode projects
43. Reusing Code The Alternatives SPM Carthage CocoaPods Manual Integration Integration Type Automatic, when opening the project Manual Automatic, when generating the project Manual Plug and Play? Yes Partially Yes No Precompiled? No Yes* No No Allows debugging? Yes No Yes Yes
44. Reusing Code The Alternatives Simple to Use Requires Manual Setup Less Control More Control CocoaPods SPM Carthage Manual Integration There’s no perfect tool. There’s a tool that best fits your needs.
45. Reusing Code Our Approach • Hybrid model: • monorepo - get rid of submodules • “Manual” integration where possible (using Tuist) • Carthage and SPM where it makes sense • Categorize in 3 types helps deciding: • Internal code that changes frequently • Internal code that changes once in a while • External code • Tuist helps a lot creating & linking projects and their targets
46. Modularization Challenge #4
47. Modularization Breaking a codebase down into small, focused, and shareable pieces, or modules.
48. Modularization The Problem(s) App Feature 2 Feature 3 Feature 1 Feature 4 HTTPClient
49. Modularization The Problem(s) App Feature 2 Feature 3 Feature 1 Feature 4 HTTPClient HTTPClient
50. Modularization The Problem(s) App Feature 2 Feature 3 Feature 1 Feature 4 HTTPClient Feature 2 Feature 3 Feature 1 Feature 4 HTTPClient
51. Modularization The Problem(s) App Feature 2 Feature 3 Feature 1 Feature 4 HTTPClient App Feature 2 Feature 3 Feature 1 Feature 4 HTTPClient
52. Modularization The Ideal, but impossible App Feature 1 Feature 2 Feature 3 Feature 4 HTTPClient
53. Modularization The Solution: Interface Targets App Feature 2 Feature 3 Feature 1 HTTPClient Feature 4 Feature 4 Interface HTTPClientInterface
54. Statically Linked! Modularization The Solution: Interface Targets App Feature 2 Feature 3 Feature 1 HTTPClient Feature 4 Feature 4 Interface HTTPClientInterface
55. Modularization The Solution: Advantages • Interfaces change less frequently • Testing • Maintenance & Replaceability
56. Modularization The Solution: Interface Targets https://swiftrocks.com/reducing-ios-build-times-by-using-interface-targets
57. Maintenance & Automation Challenge #5
58. Maintenance & Automation The Problems # Requires Time & Attention $ Manual = Mistakes Ship Products % Repetitive = Exhausting &
59. Maintenance & Automation • Write your own scripts and tools if they don’t exist yet • Swift is a fantastic language for scripting and tooling • It runs on Linux as well • SwiftUI for macOS • Setup or migration scripts Scripts & Tools
60. Maintenance & Automation Scripts & Tools - Examples hz-localizer sync
61. Maintenance & Automation Scripts & Tools - Examples
62. Maintenance & Automation Scripts & Tools - Examples
63. Maintenance & Automation Scripts & Tools - Examples PRISM
64. Maintenance & Automation Scripts & Tools - Examples
65. Maintenance & Automation Scripts & Tools - Examples
66. Maintenance & Automation Scripts & Tools - Examples SwiftGen danger.systems
67. Wrap Up
68. No more pbxproj merge conflicts Invest time analyzing build times Know the pros and cons of each package manager or manual integration Aim for a horizontal dependency tree Automate all the things Easy framework creation and error- free configuration Add warnings for long functions and expressions Decide what’s best for your case Use interface targets Use open source tools that generate code or avoid repetitive tasks More advantages come with it Modularize Avoid submodules Dependency injection Build your own tools if needed Wrap Up Xcode Project Management Maintenance & Automation Reusing Code Modularization Build Times !
69. Questions?
70. Thanks for joining! Continue the conversation @natanrolnik