Within the earlier put up I checked out among the historical past of how we packaged up our library code to be used by our fellow builders. We checked out among the advantages of static libraries versus dynamic frameworks which additionally include headers wanted by the integrator.
Now let’s dive into the steps that had been needed for me to allow SPM help on the primary few libraries DTCoreText, DTFoundation and Kvitto. It took me a number of days to iron out all of the kinks and I’d like to share with you what I discovered within the course of.
We’re used to utilizing Xcode to explain what goes right into a construct: Which recordsdata to compile, what exterior libraries to hyperlink to, what sources are wanted and in addition common construct settings just like the vary and kinds of supported platforms. Extra exactly, these settings are contained within the undertaking.pbxproj file inside your xcodeproj bundle.
With SwiftPM there isn’t a such undertaking file. Relatively the whole lot is outlined in human-readable type within the Bundle.swift file.
For some fundamental terminology: we outline sure merchandise (i.e. static library, dynamic framework, app bundle and so on, useful resource bundle, unit take a look at bundle), that relate to various targets (a bucket for a bunch of supply code recordsdata and sources). Here’s a distinction from Xcode the place goal and product is used synonymously.
Bundle Definition
Step one, and most vital one, is so as to add a package deal definition file to the foundation folder of the repository. It must be on this place as a result of Swift Packages are referenced by the repository URL and SwiftPM will solely take a look at the highest folder for Bundle.swift.
Right here’s the definition for Kvitto, for reference. This has all parts you would possibly encounter, together with a dependency on one other package deal, a few sources on high of the definition of 1 product and a number of goal.
// swift-tools-version:5.3
import PackageDescription
let package deal = Bundle(
identify: "Kvitto",
platforms: [
.iOS(.v9), //.v8 - .v13
.macOS(.v10_10), //.v10_10 - .v10_15
.tvOS(.v9), //.v9 - .v13
],
merchandise: [
.library(
name: "Kvitto",
targets: ["Kvitto"]),
],
dependencies: [
.package(url: "https://github.com/Cocoanetics/DTFoundation.git",
from: "1.7.15"),
],
targets: [
.target(
name: "Kvitto",
dependencies: [
.product(name: "DTFoundation",
package: "DTFoundation"),
],
path: "Core",
exclude: ["Info.plist"]),
.testTarget(
identify: "KvittoTests",
dependencies: ["Kvitto"],
path: "Check",
exclude: ["Info.plist"],
sources: [.copy("Resources/receipt"),
.copy("Resources/sandboxReceipt")]),
]
)The primary line would possibly solely appear to be a remark to you, however it is crucial for the swift instruments to find out what syntax parts are supported. Model 5.3 is required if in case you have sources in any goal. In the event you set that to one thing decrease you get syntax errors concerning the useful resource definitions. In the event you set that to five.3 however don’t specify useful resource definitions (for non-standard sources) you’re going to get warnings about unknown recordsdata that you must both exclude or outline as sources.
I discovered myself conflicted about that, as I had talked about within the earlier article. All code would work on Swift 5.0 and up and solely the take a look at goal has sources. I may get extra inexperienced checkmarks on Swift Bundle Index if I eliminated the .testTarget definition.
On the opposite aspect the swift instruments allow you to run thusly outlined unit exams from the command line and functioning unit exams additionally ought to depend as an indication of fine library high quality. Lastly, all people needs to be utilizing Swift 5.3 anyway as that’s the baseline customary because the launch of Xcode 12.
That’s why I selected to go away it at that.
The fundamental setup of the package deal definition is easy. You could have the package deal identify, then some minimal platform variations. Be aware that these minimal OS variations don’t imply that that would prohibit the the package deal to particular platforms.
The merchandise part defines what sort of library comes out of the construct course of. The default setting (invisible) is to supply a static library, by specifying kind: .dynamic you get a dynamic framework as an alternative. The targets array specifies which targets will get merged into the ultimate product.
I believed for a second that that is likely to be good to have the sources be added to the framework as an alternative of a separate useful resource bundle, like we’re used to. However alas the dealing with of sources stays the identical they usually get bundled right into a Product_Target.bundle. So subsequently I’d reasonably have the static library – which is able to get merged into the app binary – reasonably than having yet one more separate framework bundle contained in the app bundle.
As I defined within the earlier article, dynamic frameworks needs to be averted if the supply code for libraries is public. So we’re proud of the static library default.
The dependencies part lists the exterior reference to different packages. You specify the repository URL and the minimal variations. The proven means with from and a model would settle for all 1.x.x variations from and together with 1.7.15. There are additionally different methods to specify a precise quantity or sure ranges.
Final come the targets. We’ve got an everyday goal for the package deal and a take a look at goal for all of the unit exams. In the event you don’t specify a path then SwiftPM expects the supply code within the Sources folder beneath the goal’s folder and sources in a Sources folder. I’ve a distinct construction, so I specified a customized path.
I’ve to exclude the Data.plist for each targets as a result of that is utilized by two targets outlined contained in the Xcode undertaking. And for the take a look at goal I specify two sources to be copied with the trail relative to the goal customized path. These copy directions are needed as a result of the contained sources don’t have a sort that Xcode is aware of methods to deal with. For issues like strings recordsdata or XIBs you don’t must specify something.
Evaluate the dependencies key of each targets. On the one hand you see that I’m referencing the exterior dependency of the primary goal. Then again the take a look at goal requires the primary goal to work. That’s additionally a distinction to Xcode the place the examined code resides inside a number software, the place’s right here it’s compiled into the unit take a look at bundle.
Goal Concerns
You is likely to be questioning why there’s a distinction between merchandise and targets in SPM. One cause for that you’ve already seen: there isn’t a cause for the take a look at goal to be represented in a product. Easy packages will typically solely have one product which may solely consist of 1 goal.
Though I already discovered two extra causes, to separate code out into extra particular person targets after which additionally merchandise.
You would possibly assume that Swift Bundle Supervisor would solely all you to have code written in Swift. However you’ll be incorrect, Any language goes, additionally Goal-C and different C dialects. However SPM doesn’t will let you combine C-based languages with Swift in a single goal.
In a single undertaking I had some Goal-C code for a perform with plenty of ifs. I rewrote that in Swift solely to seek out that compiling this might take greater than a minute, in contrast to a couple seconds in Goal-C. So I selected to go away the perform because it was. The answer was to place it right into a separate Goal-C goal and refer that to an inside dependency from the primary Swift goal.
The opposite good cause for a separate goal and product was to have some frequent information mannequin code that might be utilized by inside targets and in addition through import in an app consuming my library. In locations the place the shopper would solely want the shared definitions he would import the precise module for that. Elsewhere he would import different targets which in flip may additionally make use of these definitions internally.
Every product turns into its personal module.
Resourcefulness
I discussed above you can let SPM do its personal factor on the subject of customary useful resource varieties, like localised strings, XIBs, storyboards and asset catalogs. In the event you use string localisation although, it’s important to specify the undertaking’s default language.
Different varieties it’s important to both particularly exclude or specify what needs to be achieved for it. You’ll be able to both specify a .copy for every particular person useful resource or additionally for your entire Sources folder. Since I’ve solely two take a look at recordsdata and that’s not going to alter, it wasn’t an excessive amount of work so as to add these individually.
SPM expects sources in the identical folder {that a} goal’s supply recordsdata reside in (or a sub-folder thereof). The explanation for that’s once more that there isn’t a Xcode undertaking file the place you would specify membership of sure recordsdata to particular targets. You specify what belongs the place by how it’s specified by the file system together of the package deal definition.
Say you will have a single place the place you will have localised strings recordsdata downloaded from a translation website like POEditor however you need them to be included in numerous targets. A method to realize that’s to create soft-links contained in the goal’s useful resource folders to the recordsdata. I wrote this shell script to create the lproj folders for all languages after which create the hyperlinks.
#!/bin/sh
echo "Eradicating present strings"
rm -rf ../TFMViews/Sources/*.lproj
rm -rf ../TFMExtension/Sources/*.lproj
PWD=`pwd`
for entry in *.lproj
do
echo "Linking $entry..."
mkdir ../TFMViews/Sources/$entry
ln -s ../../../Strings/$entry/TFMViews.stringsdict
../TFMViews/Sources/$entry
ln -s ../../../Strings/$entry/TFMViews.strings
../TFMViews/Sources/$entry
mkdir ../TFMExtension/Sources/$entry
ln -s ../../../Strings/$entry/TFMExtension.stringsdict
../TFMExtension/Sources/$entry
ln -s ../../../Strings/$entry/TFMExtension.strings
../TFMExtension/Sources/$entry
achievedThe identical strategy of soft-links will also be employed for Goal-C based mostly packages the place you may hyperlink to all related public headers in an embrace folder.
Platform-specific Code
Because the package deal has no facility for limiting particular supply code to particular platforms or OS variations, you’ll face the state of affairs that sure code gained’t compile for different platforms. A workaround for this limitation is using conditional compilation directives.
For instance, the whole lot that references UIKit can’t be compiled for macOS or watchOS, so I’ve a number of locations in DTCoreText or DTFoundation (each written in Goal-C) the place your entire implementation is enclosed in:
#import <TargetConditionals.h>
#if TARGET_OS_IPHONE && !TARGET_OS_WATCH
...
#endifI additionally discovered that generally I needed to additionally import the TargetConditionals header for the defines to work. Specifically sure Goal-C class extensions in DTCoreText wouldn’t be seen within the public interface if I didn’t import this header. I’ve no clarification as to why, however including the import for the header fastened it.
Contained in the Xcode Mission
The modifications for conditional compilation apart, there’s nothing you want to change in your Xcode undertaking – except you need to. The principal setup for the package deal occurs in Bundle.swift. You’ll be able to construct the package deal with issuing swift construct.
I discovered it handy so as to add a reference to the package deal contained in the Xcode undertaking as a result of this lets you debug your code within the context of being compiled for a package deal. In the event you drag any folder (containing a package deal definition) into the undertaking navigator pane, Xcode will add an area package deal reference for you, with an emblem of a cute little field.
In Xcode 12 there’s a bug that in case you try this for the undertaking folder itself, it appears to work, however when you shut the undertaking and reopen it once more, the reference turns into defunct. The way in which to repair it’s to alter the reference to “Relative to Mission” and open the folder selector through the folder button and re-select the undertaking root folder.
This additionally creates a scheme for constructing the package deal and the package deal’s merchandise change into accessible to hyperlink/embed to your app. Bundle merchandise have an icon of a greek temple. If they’re static libraries then they may get merged into the app binary, dynamic frameworks will likely be added to the app’s Frameworks folder.
Xcode additionally creates a scheme for the package deal, putting it in .swiftpm/xcode/xcshareddata/xcschemes/. I moved it into the shared schemes folder of the xcodeproj and renamed it to Kvitto-Bundle.xcscheme.
I had the watchOS platform builds on Swift Bundle Index fail as a result of xcodebuild insists on constructing all targets, together with the take a look at goal. This fails as a result of unit exams require XCTest which doesn’t excite for watchOS.
By offering an aptly named shared scheme it is going to solely construct the primary goal and I achieved inexperienced checkmarks for watchOS on SPI.
Library Unit Exams
To run the unit exams contained within the take a look at goal, all you want to do is to run swift take a look at on the command line, from the repository root folder.
Some magic was required to get that to work as a result of take a look at recordsdata required by the unit exams usually are not bundled within the .xctest bundle. For normal packages a useful resource bundle accessor is being mechanically generated, which you should use with Bundle.module.
The accessor works by figuring out the trail of the executable and setting up a bundle identify from names of package deal and goal. Within the case of unit exams the executable is xcrun contained within the Xcode.app bundle the place it has no probability of discovering the Kvitto_KittoTests.bundle.
My ugly, however purposeful, workaround for that is as follows:
func urlForTestResource(identify: String, ofType ext: String?) -> URL?
{
let bundle = Bundle(for: kind(of: self))
#if SWIFT_PACKAGE
// there's a bug the place Bundle.module factors to the trail of xcrun contained in the Xcode.app bundle, as an alternative of the take a look at bundle
// that aborts unit exams with message:
// Deadly error: couldn't load useful resource bundle: /Purposes/Xcode.app/Contents/Developer/usr/bin/Kvitto_KvittoTests.bundle: file KvittoTests/resource_bundle_accessor.swift, line 7
// workaround: attempt to discover the useful resource bundle on the construct path
let buildPathURL = bundle.bundleURL.deletingLastPathComponent()
guard let resourceBundle = Bundle(url: buildPathURL.appendingPathComponent("Kvitto_KvittoTests.bundle")),
let path = resourceBundle.path(forResource: identify, ofType: ext) else
{
return nil
}
return URL(fileURLWithPath: path)
#else
guard let path = bundle.path(forResource: identify, ofType: ext) else
{
return nil
}
return URL(fileURLWithPath: path)
#endif
}This depends on the truth that the useful resource bundle will likely be created parallel to the xctest bundle, in the identical construct folder. The #if SWIFT_PACKAGE conditional compilation will solely be added if this code is constructed as a part of a swift package deal. With this workaround, the earlier mechanisms of working the unit take a look at scheme through Xcode continues to work.
The beauty of Swift being open supply, is that we will additionally examine the code for the useful resource accessor on GitHub. It seems that the talked about bug has already been addressed there. The repair was made too late to make it into Swift 5.3 in Xcode 12 however has been confirmed to be current in Xcode 12.2.
Conclusion
I discover that the evolution of Swift Bundle Supervisor as progressed sufficiently to start out including help for it to my libraries. It’s attainable and advisable to take action along with different methods of integration, like Xcode subproject, Cocoapods or Carthage.
Probably the most annoying limitation remaining is that you simply can not restrict targets to sure platforms or specify a variety of supported OS variations per goal. However these can simply be labored round with conditional compilation directives.
The standard standards partially enforced by the Swift Bundle Index coupled with the discoverability of parts additionally make it engaging for library distributors to contemplate supporting Swift Bundle Supervisor. Having the dependency administration taken care of by Xcode is the best characteristic of all.
Additionally printed on Medium.
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