Scaling Your iOS Codebase

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Scaling Your iOS Codebase Challenges and approaches from our experience at Houzz

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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

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iOS @ Houzz: an overview

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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

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+15 Internal Frameworks Swift + ObjC iOS at Houzz 2 Apps 6 App Extensions

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iOS at Houzz In a nutshell

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Sounds familiar?

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Agenda 5 Challenges Xcode Project Management Maintenance & Automation Reusing Code Modularization Build Times !

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Xcode Project Management Challenge #1

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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)

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Xcode Project Management The Problem ! Hard to read & maintain " Doesn’t reﬂect ﬁle system # Settings & Linking error prone $ Larger teams %& Multiple branches

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Xcode Project Management

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Xcode Project Management The Solution Describe your project Sources, Resources, Targets, Settings…

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Xcode Project Management The Solution Describe your project Sources, Resources, Targets, Settings…

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Xcode Project Management The Solution

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• 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

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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

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Xcode Project Management Tuist

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Long Build Times Challenge #2

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Long Build Times https://xkcd.com/303/

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Long Build Times The Problem !" Code Changes ! Clear Derived Data git Git Operations

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Long Build Times The Reasons • Massive ﬁles • Mixed Obj-C and Swift code • Long functions • Long expressions & type inference • Build phases

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Long Build Times Solutions

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Long Build Times Solutions

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Long Build Times Solutions

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Long Build Times Solutions

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• 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

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• 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

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• Delete unused code • Reevaluate dependencies constantly • Show build times in Xcode: Long Build Times Solutions $ defaults write com.apple.dt.Xcode ShowBuildOperationDuration -bool YES

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• 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

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Reusing Code Challenge #3

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Reusing Code The Problem Target Membership My MVP App ✓ Model.swift CoreDataStack.swift Networking.swift

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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

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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

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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

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Reusing Code The Alternatives 1. Package Managers: Swift Package Manager, CocoaPods, Carthage 2. Manual Integration: Workspace with multiple Xcode projects

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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

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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.

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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

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Modularization Challenge #4

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Modularization Breaking a codebase down into small, focused, and shareable pieces, or modules.

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Modularization The Problem(s) App Feature 2 Feature 3 Feature 1 Feature 4 HTTPClient

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Modularization The Problem(s) App Feature 2 Feature 3 Feature 1 Feature 4 HTTPClient HTTPClient

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Modularization The Problem(s) App Feature 2 Feature 3 Feature 1 Feature 4 HTTPClient Feature 2 Feature 3 Feature 1 Feature 4 HTTPClient

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Modularization The Problem(s) App Feature 2 Feature 3 Feature 1 Feature 4 HTTPClient App Feature 2 Feature 3 Feature 1 Feature 4 HTTPClient

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Modularization The Ideal, but impossible App Feature 1 Feature 2 Feature 3 Feature 4 HTTPClient

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Modularization The Solution: Interface Targets App Feature 2 Feature 3 Feature 1 HTTPClient Feature 4 Feature 4 Interface HTTPClientInterface

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Statically Linked! Modularization The Solution: Interface Targets App Feature 2 Feature 3 Feature 1 HTTPClient Feature 4 Feature 4 Interface HTTPClientInterface

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Modularization The Solution: Advantages • Interfaces change less frequently • Testing • Maintenance & Replaceability

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Modularization The Solution: Interface Targets https://swiftrocks.com/reducing-ios-build-times-by-using-interface-targets

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Maintenance & Automation Challenge #5

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Maintenance & Automation The Problems # Requires Time & Attention $ Manual = Mistakes Ship Products % Repetitive = Exhausting &

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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

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Maintenance & Automation Scripts & Tools - Examples hz-localizer sync

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Maintenance & Automation Scripts & Tools - Examples

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Maintenance & Automation Scripts & Tools - Examples

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Maintenance & Automation Scripts & Tools - Examples PRISM

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Maintenance & Automation Scripts & Tools - Examples

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Maintenance & Automation Scripts & Tools - Examples

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Maintenance & Automation Scripts & Tools - Examples SwiftGen danger.systems

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Wrap Up

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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 !