Ruthlessly Simple Dependency Management with Carthage

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What Why How to use it How it works

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Justin Spahr-Summers @jspahrsummers

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The Problem

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Dependencies in Cocoa (historically) 1. Copied source files 2. Zipped binaries 3. SVN externals, Git submodules 4. Git subtrees

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Dependencies on other platforms 1. Dependency managers

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Our Problem

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GitHub for Mac has what could be called “excessively nested submodules.” 1 Me, late 2014

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GitHub for Mac Mantle Squirrel OctoKit ReactiveCocoa ReactiveViewModel

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Why not use CocoaPods?

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Podspecs

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Less control

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Centralized

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@robrix @mdiep @keithduncan @alanjrogers

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Our goals ⁶ ⁵ 1. Pick compatible versions for all dependencies 2. Check out dependencies with Git 3. Build frameworks with Xcode

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Using Carthage

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Step 1: Create a Cartfile github "Mantle/Mantle" ~> 1.5 github "ReactiveCocoa/ReactiveCocoa" >= 2.4.7 github "ReactiveCocoa/ReactiveCocoaLayout" == 0.5.2

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Step 2: Run Carthage $ carthage update *** Fetching Mantle *** Fetching ReactiveCocoa *** Fetching ReactiveCocoaLayout *** Fetching Archimedes *** Downloading Archimedes at "1.1.4" *** Downloading Mantle at "1.5.4" *** Downloading ReactiveCocoa at "v2.4.7" *** Downloading ReactiveCocoaLayout at "0.5.2"

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Step 3: Link Frameworks

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Step 4: Strip architectures (iOS only)

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That’s it!

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“Ruthlessly Simple”

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Easy: familiar or approachable Simple: fewer concepts and concerns1 1 See Rich Hickey’s talk, Simple Made Easy

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CocoaPods is easy Carthage is simple

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Simpler tools are…

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Easier to understand

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Easier to maintain Easier to contribute to

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More flexible More composable

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Enhanced when other tools improve

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Behind the Scenes

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Parse the Cartfile Resolve the dependency graph Download all dependencies Build each framework

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! Parsing Parse OGDL into a list of dependencies github "ReactiveCocoa/ReactiveCocoa" >= 2.4.7

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! Parsing Parse OGDL into a list of dependencies github "ReactiveCocoa/ReactiveCocoa" >= 2.4.7 Determine the type of each dependency github "ReactiveCocoa/ReactiveCocoa"

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! Parsing Parse OGDL into a list of dependencies github "ReactiveCocoa/ReactiveCocoa" >= 2.4.7 Determine the type of each dependency github "ReactiveCocoa/ReactiveCocoa" Parse any Semantic Version >= 2.4.7

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㿃 Resolving CarthageDemo/Cartfile: github "Mantle/Mantle" ~> 1.5 github "ReactiveCocoa/ReactiveCocoa" >= 2.4.7 github "ReactiveCocoa/ReactiveCocoaLayout" == 0.5.2

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㿃 Resolving Create a graph of the latest dependency versions Demo ReactiveCocoa 3.0 ReactiveCocoaLayout 0.5.2 Mantle 1.5.4

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㿃 Resolving Insert dependency Cartfiles into the graph Demo ReactiveCocoa 3.0 ReactiveCocoaLayout 0.5.2 Mantle 1.5.4 2.4.7 Archimedes 1.1.4

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㿃 Resolving If requirements conflict, throw out the graph Demo ReactiveCocoa 3.0 ReactiveCocoaLayout 0.5.2 Mantle 1.5.4 2.4.7 Archimedes 1.1.4

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㿃 Resolving Try a new graph with the next possible version Demo ReactiveCocoa 2.4.7 ReactiveCocoaLayout 0.5.2 Mantle 1.5.4

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㿃 Resolving Repeat until a valid graph is found Demo ReactiveCocoa 2.4.7 ReactiveCocoaLayout 0.5.2 Mantle 1.5.4 2.4.7 Archimedes 1.1.4

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! Downloading 1. Fetch the repository into Carthage’s cache

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! Downloading 1. Fetch the repository into Carthage’s cache 2. Copy the right version into Carthage/Checkouts

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! Building 1. Symlink Carthage/Build into the dependency folder

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! Building 1. Symlink Carthage/Build into the dependency folder 2. List framework schemes from the .xcodeproj

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! Building 1. Symlink Carthage/Build into the dependency folder 2. List framework schemes from the .xcodeproj 3. Build each scheme for all supported architectures

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! Building 1. Symlink Carthage/Build into the dependency folder 2. List framework schemes from the .xcodeproj 3. Build each scheme for all supported architectures 4. Combine multiple architectures with lipo

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✨ BONUS: Prebuilt binaries! ✨ *** Downloading ReactiveCocoa at "v2.4.7"

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CarthageKit

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Technical Choices

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Dynamic frameworks vs. static libraries 4 iOS 8+ only 4 Can include resources 4 Self-contained and ready-to-use 4 Avoid duplicate symbol errors 4 Required for Swift

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Swift vs. Objective-C 4 Type safety 4 Value types (especially enums) 4 Much faster to write 4 Better modularization 4 The Next Big Thing™

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ReactiveCocoa 4 Simplifies networking (with the GitHub API) 4 Simplifies the dependency resolver 4 Simplifies shelling out, via ReactiveTask 4 Carthage helps test RAC 3.0 in the real world

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1.0

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Per-project settings

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Review CarthageKit API Review command line flags

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Profit!!! !

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What Why How to use it How it works

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Questions? Comments? Slides and notes, plus my demo project, are available at: https://github.com/jspahrsummers/carthage-talk Thanks to everyone who reviewed this presentation, and to Realm for inviting me to speak!2 2 ❤ Matt Diephouse, Rob Rix, Alan Rogers, Keith Duncan, Nacho Soto, Tom Brow, James Lawton, Arwa Jumkawala, JP Simard, Tim Anglade, Brendan Forster, Benjamin Encz, Robert Böhnke, and you!