Ruthlessly Simple Dependency Management with Carthage

Carthage is a new dependency manager for Objective-C and Swift projects, intended to be the simplest way to add frameworks to a Cocoa application. Carthage works by delegating tasks to Xcode and Git, minimizing new concepts as much as possible, so you can continue to use the tools you’re already familiar with.

This talk will explain what Carthage is and how to use it, then dive into the philosophy of ruthless simplicity that inspired the project. We’ll also compare and contrast Carthage with CocoaPods, the original dependency manager for Cocoa. Finally, we’ll explore how Carthage is architected under-the-hood, and the benefits we’ve seen from writing it completely in Swift.

Transcript

1. Ruthlessly Simple Dependency Management with Carthage
2. What Why How to use it How it works
3. Justin Spahr-Summers @jspahrsummers
4. The Problem
5. Dependencies in Cocoa (historically) 1. Copied source files 2. Zipped binaries 3. SVN externals, Git submodules 4. Git subtrees
6. Dependencies on other platforms 1. Dependency managers
7. Our Problem
8. GitHub for Mac has what could be called “excessively nested submodules.” 1 Me, late 2014
9. GitHub for Mac Mantle Squirrel OctoKit ReactiveCocoa ReactiveViewModel
10. Why not use CocoaPods?
11. Podspecs
12. Less control
13. Centralized
14. !
15. @robrix @mdiep @keithduncan @alanjrogers
16. Our goals ⁶ ⁵ 1. Pick compatible versions for all dependencies 2. Check out dependencies with Git 3. Build frameworks with Xcode
17. Using Carthage
18. Step 1: Create a Cartfile github "Mantle/Mantle" ~> 1.5 github "ReactiveCocoa/ReactiveCocoa" >= 2.4.7 github "ReactiveCocoa/ReactiveCocoaLayout" == 0.5.2
19. 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"
20. Step 3: Link Frameworks
21. Step 4: Strip architectures (iOS only)
22. That’s it!
23. “Ruthlessly Simple”
24. Easy: familiar or approachable Simple: fewer concepts and concerns1 1 See Rich Hickey’s talk, Simple Made Easy
25. CocoaPods is easy Carthage is simple
26. Simpler tools are…
27. Easier to understand
28. Easier to maintain Easier to contribute to
29. More flexible More composable
30. Enhanced when other tools improve
31. Behind the Scenes
32. Parse the Cartfile Resolve the dependency graph Download all dependencies Build each framework
33. ! Parsing Parse OGDL into a list of dependencies github "ReactiveCocoa/ReactiveCocoa" >= 2.4.7
34. ! Parsing Parse OGDL into a list of dependencies github "ReactiveCocoa/ReactiveCocoa" >= 2.4.7 Determine the type of each dependency github "ReactiveCocoa/ReactiveCocoa"
35. ! 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
36. 㿃 Resolving CarthageDemo/Cartfile: github "Mantle/Mantle" ~> 1.5 github "ReactiveCocoa/ReactiveCocoa" >= 2.4.7 github "ReactiveCocoa/ReactiveCocoaLayout" == 0.5.2
37. 㿃 Resolving Create a graph of the latest dependency versions Demo ReactiveCocoa 3.0 ReactiveCocoaLayout 0.5.2 Mantle 1.5.4
38. 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
39. 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
40. 㿃 Resolving Try a new graph with the next possible version Demo ReactiveCocoa 2.4.7 ReactiveCocoaLayout 0.5.2 Mantle 1.5.4
41. 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
42. ! Downloading 1. Fetch the repository into Carthage’s cache
43. ! Downloading 1. Fetch the repository into Carthage’s cache 2. Copy the right version into Carthage/Checkouts
44. ! Building 1. Symlink Carthage/Build into the dependency folder
45. ! Building 1. Symlink Carthage/Build into the dependency folder 2. List framework schemes from the .xcodeproj
46. ! Building 1. Symlink Carthage/Build into the dependency folder 2. List framework schemes from the .xcodeproj 3. Build each scheme for all supported architectures
47. ! 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
48. ! 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 5. Copy the built frameworks into Carthage/Build
49. ✨ BONUS: Prebuilt binaries! ✨ *** Downloading ReactiveCocoa at "v2.4.7"
50. CarthageKit
51. Technical Choices
52. 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
53. 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™
54. 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
55. 1.0
56. Per-project settings
57. Review CarthageKit API Review command line flags
58. Profit!!! !
59. What Why How to use it How it works
60. 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!