Include System Libraries Using Swift Package Manager Or CocoaPods

I’m currently using swift package manager to build a framework for an iOS project.  Why? Because I like the clean, modular approach, no need to have an Xcode project and I find it faster for CI testing.

Unfortunately swift package manager doesn’t work for the iOS project.  And since my team is already familiar with CocoaPods that is what the iOS project is using.

Now I will explain how I included a system library inside a Swift framework that is then used in an iOS project with CocoaPods.

I’ll show you how I setup CommonCrypto to use Swift Package Manager and CocoaPods.

For Swift Package Manager:

• A. Create a git repo for the swift package wrapper around the system library.   
  1. Add a module.modulemap file to the repo and add the system header you are wrapping.
     module CCommonCrypto [system] {
header "/usr/include/CommonCrypto/CommonCrypto.h"
export *
}

  2.  Add Package.swift file to repo
import PackageDescription
let package = Package(
name: "CCommonCrypto"
)
  3.  Commit the files and add a tag to them (Swift Packages need a tag to be used)
git tag 0.0.1
git push origin 0.0.1
(you can overwrite previous tag by using the "-f" flag on both of those commands)
• B. Create another repo for the Swift Package that will use the system package wrapper.
  1. Create the Package.swift file and add the repo created in step 1 as a dependency.
     
import PackageDescription
let package = Package(
name: "CommonCrypto",
targets: [
Target(name: "CommonCrypto"),
],
dependencies: [
.Package(url: "https://github.com/kmussel/ccommoncrypto.git", "0.0.1"),
]
)
  2. Add the “Sources” folder and a subfolder named the same thing you named your target in the Package.swift file
     Sources -> CommonCrypto
  3. Inside the subfolder (CommonCrypto in this case) add all your swift files that you want to use.
     1.  In each file that you want to use the dependency package import that package using the name from its Package.swift file
        import CCommonCrypto

Now you can create another Swift Package and include Repo 2 as a dependency and when you run “swift build” it will download and include the dependencies

You can also run “swift package generate-xcodeproj” if you want to use the Xcode project.

Getting the Swift Package to Work with CocoaPods:

• C.  Repo 1 is not needed.  We just need to update Repo 2 with necessary CocoaPod files.
  1.  Add another subfolder under the Subfolder we created in Step B.2. The name of the subfolder should match the name of the Package from step A.2.  This is so CocoaPods will recognize the import statement from step B.3.1.
  2. Copy the module.modulemap file from step A.1. into this subfolder.

  3. Create another subfolder in the root directory.  It can be named anything you want but I called it “CocoaPods” since it is only used for that.

  4. Inside the “CocoaPods” directory you will create multiple subfolders for each target you want this package to target.
     ie. iphoneos, iphonesimulator, macosx, etc

  5. Create the files module.map under each of the subfolders you just created pointing to the correct system headers
     CocoaPods -> iphoneos -> module.map
module CCommonCrypto [system] {
header "/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS10.1.sdk/usr/include/CommonCrypto/CommonCrypto.h"
export *
}
  6. Create the Podspec file for it
     1. Our source_files will just be the .swift files inside the Sources directory.  These files are added to the Xcode project.
        s.source_files = "Sources/**/*.swift"
     2. Normally any file not in the source_files will be removed but we need the project to be able to access our “CocoaPods” directory to know which files to include.  To keep the “CocoaPods” directory without adding it to the project we use the “preserve_paths” command to keep the “CocoaPods” directory.
        s.preserve_paths = 'CocoaPods/**/*'
     3. We then tell Xcode where the include paths are for each sdk.  CocoaPods installs it in the PODS_ROOT directory and under the subdirectory named the same as the name of this Podspec.
        s.pod_target_xcconfig = {
'SWIFT_INCLUDE_PATHS[sdk=iphoneos*]' => '$(PODS_ROOT)/CommonCrypto/CocoaPods/iphoneos',
'SWIFT_INCLUDE_PATHS[sdk=iphonesimulator*]' => '$(PODS_ROOT)/CommonCrypto/CocoaPods/iphonesimulator',
'SWIFT_INCLUDE_PATHS[sdk=macosx*]' => '$(PODS_ROOT)/CommonCrypto/CocoaPods/macosx'
}

     4. The next thing is that the header file in each of the module.map files probably won’t be the same for each user.  We need to change it for the user when they install via pod install.  We create a script to do this and execute it using the prepare_command in cocoa pods.  For example, my path is “/Applications/Xcode-beta.app/Contents/Developer/” so this script replaces the default to that.  I grabbed the script from this site. But should probably should modify the script to handle sdk versions too.
        s.prepare_command = <<-CMD
./CocoaPods/injectXcodePath.sh
CMD


 Now you can include Repo 2 in the Podfile of your iOS project.

The entire Podspec:

You can see the entire CommonCrypto example here:

https://github.com/kmussel/commoncrypto
https://github.com/kmussel/ccommoncrypto