As of Xcode 12, Apple has matured Swift Package deal Manger to a level the place it is smart so as to add help for Swift packages to your libraries. There are nonetheless a couple of stumbling stones on the trail which haven’t any apparent answer. So I determine, I’d share with you ways I obtained round them after I not too long ago added SPM help to DTCoreText, DTFoundation and Kvitto.
Earlier than SwiftPM, my basic strategy for a library could be to have all library code in a `Core` subfolder, with a `Supply` folder containing code which will get compiled and a Assets folder for all types of sources, like for instance asset catalogs or XIB information.
A Little bit of Historical past
For the primary 7 iOS variations the product of this product may solely be a static library, Apple solely launched the power to create dynamic frameworks for Goal-C as of iOS 8. With Swift it was the opposite method round: you may solely have dynamic frameworks with Swift code. For the primary 4 variations of Swift the ABI (Software Binary Interface) was an excessive amount of in flux to permit a statically linked product. With Swift 5, in 2019, we lastly obtained the required stability and thus Xcode gained the power to supply static libraries containing Swift code. That is additionally the primary cause why Xcode at all times added a bunch of dylibs to your apps, containing Swift wrappers to all of the frameworks your app is likely to be interfacing. These dynamic libraries are the third sort of libraries we have now encountered thus far.
Oh boy, I keep in mind all of the hackery we needed to do to supply a „faux“ framework that was basically a fats static library (with slices for all supported processors) and all public headers. We might that in order that someone utilizing our library may drop it simply into their challenge and have all uncovered interfaces be seen. In Goal-C you would want to have the header information out there for public features and lessons contained within the library. These `.framework` bundles supplied a pleasant encapsulation of that, in order that it was virtually like dealing with a single bundle including a third-party framework to your app.
Dynamic frameworks – in actual life, on system – truly don’t comprise any headers any extra as these grow to be ineffective after compiling. The primary good thing about first-party dynamic frameworks is that Apple can have their APIs and code shared between all apps put in on the system. The one and solely UIKit framework – put in as a part of iOS – is being accessed by and dynamically linked to all put in iOS apps. Solely a single occasion is current in RAM at any time. Customized frameworks can’t be shared between a number of apps as a consequence of all apps being contained in their very own little sandbox. Each iOS app containing DTCoreText for instance has to have its distinctive copy of it inside its app bundle. If an app has quite a lot of third-party frameworks that means of loading all frameworks into reminiscence and dynamically linking can noticeably decelerate app launch.
Swift By no means Had Headers
With the improvements introduced with Swift additionally added the idea of modules to Xcode. The Swift Programming Language Web site presents this definition of modules.
A module is a single unit of code distribution—a framework or software that’s constructed and shipped as a single unit and that may be imported by one other module with Swift’s import key phrase. Every construct goal (equivalent to an app bundle or framework) in Xcode is handled as a separate module in Swift.
If you import a module in your code, then Xcode in some way magically is aware of all in regards to the public interfaces contained in it, with out ever having to have a separate header file. I don’t understand how precisely that works, however I’m glad that it does!
It was the issue of discovering and integrating third-party libraries into your codebase, that Cocoapods was invented to resolve. The primary public launch of it was virtually precisely 9 years in the past, in September 2011. With the default settings – not utilizing frameworks – Cocoapods would compile the third-party code and merge it with your individual, leading to a single monolithic app binary. And naturally it might handle all these Goal-C headers for you. When you added use_frameworks! to your Podfile then the technique would change to as a substitute create a framework/module per pod/library. And that may be the requirement for while you have been utilizing exterior libraries written in Swift, or so I assumed …
I’ve at all times used that in apps I’m engaged on which use Cocoapods for dependencies. Think about me rambling on to a consumer of mine in regards to the disadvantages of dynamic frameworks, attempting to persuade him of the advantages of Swift Package deal Supervisor. Think about my shock after we inspected his app’s bundle, solely to seek out however a single framework in there. All of the third get together code he had ended up fused with the app binary, my library – written in Swift and built-in by way of git submodule and Xcode sub challenge – leading to the one dynamic framework in his app.
By default, CocoaPods had been doing all alongside what we all know to be the smarter alternative: if third get together code is accessible, to merge the item code it into the app binary. After all closed-source frameworks that are solely out there as dynamic framework binaries go away you with out this feature. Personally I attempt to keep away from these, just like the satan avoids holy water.
Oh and I additionally would be the first to confess that I may by no means heat myself to Carthage. I’ve by no means checked out it. So far as I perceive, the distinction in strategy versus CocoaPods is that Carthage solely wants a repo URL so as to add a part, whereas CocoaPods wants a Podspec and can generate an Xcode workspace for you the place all dependencies are arrange in a Pods challenge. I consider it is likely to be this workspace wizardry that may put some folks off Cocoapods.
Resourceful Swift Packages
Earlier than the present model 5.3 of SPM the 2 massive remaining ache factors have been the dearth of dealing with of sources and no help for distributing binaries as packages. These have now been remedied and what’s the very best half is that Swift packages now have correct integration in Xcode 12.
One other massive benefit that CocoaPods had over different dependency managers was the existence of the “trunk”, a centralised repository of accessible pods. There you may search and discover libraries that may fulfil sure wants of yours. One other necessary side could be that for a model to be launched on the CocoaPods trunk, you would need to “lint” your pod spec which might validate the syntax and ensure that the library builds with out errors or warnings.
Apple (and the SwiftPM open supply neighborhood) have labored on sharpening the instrument itself. However the central repository with validation side of bundle administration was unfilled. Till Dave Verver stepped and established the Swift Package deal Index. In his personal phrases:
The Swift Package deal Index is a search engine for packages that help the Swift Package deal Supervisor.
However this web site isn’t merely a search instrument. Selecting the best dependencies is about extra than simply discovering code that does what you want. Are the libraries you’re selecting properly maintained? How lengthy have they been in growth? Are they properly examined? Selecting high-quality packages is difficult, and the Swift Package deal Index helps you make higher selections about your dependencies.
Dave launched the SwiftPM Library within the fall of 2019 which in June 2020 obtained re-engineered because the Swift Package deal Index which we use in the present day.
It was this implementation of a central index, focussing on bundle high quality, that pushed me over the sting to lastly begin embracing SPM. With CocoaPods it has been a tedium to arrange a CI server to maintain constructing your libraries for each change to ensure that nothing breaks. Against this, SPI builds your bundle with Swift variations 4.0, 5.0, 5.1, 5.2, 5.3 for iOS, macOS Intel, macOS ARM, Linux, tvOS and watchOS and can then present on the bundle’s web page the place that labored.
This web page provides a really good overview by which builders can achieve an thought as to the standard of this library. And for us challenge house owners it supplies an incentive to attempt to maximise the variety of inexperienced checkmarks you see.
SPI nonetheless tracks 5.3 as “beta” though Xcode 12 has gone gold a month in the past. The reason is that Apple has rushed out Xcode 12 and the finalised help for constructing common apps that may additionally run on Apple Silicon will likely be in Xcode 12.2 – out there later this yr.
I additionally like how SPI tracks each the newest steady launch (by way of tag on grasp) in addition to the progress on the develop department. I needed for these builds to be coming sooner, ideally proper after pushing modifications to the GitHub repo, however generally it could take a very long time for the builds to be scheduled. Additionally a strategy to retry a failed construct could be very good, as we’re used to from Travis-CI or GitLab-CI.
Conclusion
At this level I needed to enter the issues I discovered so removed from including SPM to a few of my libraries, however I’m nonetheless combating with SPI over a few of these coveted checkmarks. Additionally this text has already turned out longer than I needed it to, that I’ll do this within the subsequent one.
Let me know if that’s of curiosity to you, by dropping me a tweet. Are you contemplating including SPM your self? Which half did you battle with?
Half 2 is right here.
Additionally printed on Medium.
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