Including Swift Bundle Supervisor Help – Half 2

Spread the love

Within the earlier submit I checked out a few of the historical past of how we packaged up our library code to be used by our fellow builders. We checked out a few of 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 vital for me to allow SPM assist 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 realized 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 likewise normal construct settings just like the vary and varieties of supported platforms. Extra exactly, these settings are contained within the venture.pbxproj file inside your xcodeproj bundle.

With SwiftPM there is no such thing as a such venture file. Reasonably all the things is outlined in human-readable type within the Bundle.swift file.

For some primary 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 a lot of 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 basis 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 have a look at the highest folder for Bundle.swift.

Right here’s the definition for Kvitto, for reference. This has all parts you may 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: [
            name: "Kvitto",
            targets: ["Kvitto"]),
    dependencies: [
        .package(url: "", 
		from: "1.7.15"),
    targets: [
            name: "Kvitto",
            dependencies: [
                .product(name: "DTFoundation", 
				package: "DTFoundation"),
            path: "Core",
            exclude: ["Info.plist"]),
            identify: "KvittoTests",
            dependencies: ["Kvitto"],
            path: "Take a look at",
            exclude: ["Info.plist"],
            sources: [.copy("Resources/receipt"),

The primary line may solely appear like a remark to you, however it can be crucial for the swift instruments to find out what syntax parts are supported. Model 5.3 is required when you’ve got sources in any goal. Should you set that to one thing decrease you get syntax errors relating to the useful resource definitions. Should 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 need to 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 facet the swift instruments allow you to run thusly outlined unit checks from the command line and functioning unit checks additionally ought to rely as an indication of excellent library high quality. Lastly, everyone needs to be utilizing Swift 5.3 anyway as that’s the baseline commonplace for the reason that launch of Xcode 12.

That’s why I selected to depart it at that.

The essential setup of the package deal definition is easy. You will 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 sort: .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 could 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 and so they get bundled right into a Product_Target.bundle. So subsequently I’d fairly have the static library – which is able to get merged into the app binary – fairly 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 approach 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 a daily goal for the package deal and a take a look at goal for all of the unit checks. Should 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 Assets folder. I’ve a special construction, so I specified a customized path.

I’ve to exclude the Information.plist for each targets as a result of that is utilized by two targets outlined contained in the Xcode venture. 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 vital as a result of the contained sources don’t have a sort that Xcode is aware of the best way 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 bunch utility, the place’s right here it’s compiled into the unit take a look at bundle.

Goal Issues

You could be questioning why there’s a distinction between merchandise and targets in SPM. One motive for that you’ve already seen: there is no such thing as a motive 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 may assume that Swift Bundle Supervisor would solely all you to have code written in Swift. However you’d be flawed, Any language goes, additionally Goal-C and different C dialects. However SPM doesn’t let you combine C-based languages with Swift in a single goal.

In a single venture I had some Goal-C code for a operate with loads of ifs. I rewrote that in Swift solely to search out that compiling this might take greater than a minute, in contrast to a couple seconds in Goal-C. So I selected to depart the operate because it was. The answer was to place it right into a separate Goal-C goal and refer that to an inner dependency from the primary Swift goal.

The opposite good motive for a separate goal and product was to have some widespread information mannequin code that might be utilized by inner targets and likewise 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.


I discussed above you can let SPM do its personal factor relating to commonplace useful resource sorts, like localised strings, XIBs, storyboards and asset catalogs. Should you use string localisation although, you must specify the venture’s default language.

Different sorts you must both particularly exclude or specify what needs to be accomplished for it. You possibly can both specify a .copy for every particular person useful resource or additionally for your complete Assets folder. Since I’ve solely two take a look at recordsdata and that’s not going to vary, 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 rationale for that’s once more that there is no such thing as a Xcode venture file the place you might 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 might have a single place the place you might have localised strings recordsdata downloaded from a translation web site like POEditor however you need them to be included in several targets. A method to attain 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.


echo "Eradicating present strings"
rm -rf ../TFMViews/Assets/*.lproj
rm -rf ../TFMExtension/Assets/*.lproj


for entry in *.lproj
  echo "Linking $entry..."

  mkdir ../TFMViews/Assets/$entry
  ln -s ../../../Strings/$entry/TFMViews.stringsdict 
  ln -s ../../../Strings/$entry/TFMViews.strings 

  mkdir ../TFMExtension/Assets/$entry
  ln -s ../../../Strings/$entry/TFMExtension.stringsdict 
  ln -s ../../../Strings/$entry/TFMExtension.strings 


The identical strategy of soft-links will also be employed for Goal-C based mostly packages the place you’ll be able to 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 received’t compile for different platforms. A workaround for this limitation is using conditional compilation directives.

For instance, all the things that references UIKit can’t be compiled for macOS or watchOS, so I’ve a couple of locations in DTCoreText or DTFoundation (each written in Goal-C) the place your complete implementation is enclosed in:

#import <TargetConditionals.h>


I 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 mounted it.

Contained in the Xcode Mission

The modifications for conditional compilation apart, there’s nothing that you must change in your Xcode venture – except you need to. The principal setup for the package deal occurs in Bundle.swift. You possibly can 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 venture as a result of this lets you debug your code within the context of being compiled for a package deal. Should you drag any folder (containing a package deal definition) into the venture 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 if you happen to do this for the venture folder itself, it appears to work, however when you shut the venture and reopen it once more, the reference turns into defunct. The best way to repair it’s to vary the reference to “Relative to Mission” and open the folder selector through the folder button and re-select the venture root folder.

This additionally creates a scheme for constructing the package deal and the package deal’s merchandise change into out there to hyperlink/embed to your app. Bundle merchandise have an icon of a greek temple. If they’re static libraries then they’ll get merged into the app binary, dynamic frameworks can be added to the app’s Frameworks folder.

Xcode additionally creates a scheme for the package deal, inserting 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 checks require XCTest which doesn’t excite for watchOS.

By offering an aptly named shared scheme it should solely construct the primary goal and I achieved inexperienced checkmarks for watchOS on SPI.

Library Unit Assessments

To run the unit checks contained within the take a look at goal, all that you must do is to run swift take a look at on the command line, from the repository root folder.

Results of working the Kvitto unit checks from the command line

Some magic was required to get that to work as a result of take a look at recordsdata required by the unit checks usually are not bundled within the .xctest bundle. For normal packages a useful resource bundle accessor is being robotically generated, which you need to 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 checks the executable is xcrun contained within the bundle the place it has no likelihood of discovering the Kvitto_KittoTests.bundle.

My ugly, however useful, workaround for that is as follows:

func urlForTestResource(identify: String, ofType ext: String?) -> URL?
	let bundle = Bundle(for: sort(of: self))
	// there's a bug the place Bundle.module factors to the trail of xcrun contained in the bundle, as an alternative of the take a look at bundle
	// that aborts unit checks with message:
	//   Deadly error: couldn't load useful resource bundle: /Purposes/ 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)
	guard let path = bundle.path(forResource: identify, ofType: ext) else
		return nil
	return URL(fileURLWithPath: path)

This depends on the truth that the useful resource bundle can 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.


I discover that the evolution of Swift Bundle Supervisor as progressed sufficiently to begin including assist 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 think about supporting Swift Bundle Supervisor. Having the dependency administration taken care of by Xcode is the best characteristic of all.

Additionally printed on Medium.

Classes: Administrative

Leave a Reply

Your email address will not be published. Required fields are marked *