Kotlin plugin to support Swift Package dependencies

This gradle plugin provides two-way interoperability between Kotlin dependencies and Kotlin-based Swift Package Multiplatform.

Add plugin

plugins {
    java
    kotlin("multiplatform")
    id("com.doublesymmetry.kotlin-native-spm")
}

Using Swift package dependency as a Kotlin library

1. Define multiplatform targets (macos, ios, tvos, watchos).

2. Declare a spm section with all the necessary package dependencies for each platform.

3. Add package dependencies with URL link, version and name. This name would be used as an import in the Kotlin project.

   build.gradle.kts example:

   kotlin {
       macosX64()
   
       spm {
           macos("11") {
               dependencies {
                   packages(
                       url = "https://github.com/AFNetworking/AFNetworking.git",
                       version = "4.0.0",
                       name = "AFNetworking"
                   )
               }
           }
       }
   }

4. Run the spmImport gradle tasks for each dependency and platform.

   ./gradlew spmImport

NOTE: At the moment, Kotlin is not directly compatible with Swift. Therefore, you can only connect Objective-C libraries that have a Swift package file.

Using the Kotlin library as a Swift Package dependency

To create a Kotlin library as a swift package dependency, you need to add the Kotlin multiplatform settings and specify the name of the resulting library (this is the name that will be used during import).

1. Extend targets configuration with framework baseName (KlibIOS in this example. Could be any). This name would be used as Swift package name in XCode project.

2. Declare a spm section with needed platforms. Note that you can add Swift package dependencies too (see first section).

   build.gradle.kts example:

   kotlin {
       iosArm64 {
           binaries {
               framework {
                   baseName = "KlibIOS"
               }
           }
       }
   
       spm {
           ios("11") { }
       }
   }

3. Create xcframework

   ./gradlew bundleXCFramework

   XCFramework will be located in build/spmUtils/xcframework/KotlinLibrary.xcframework

4. Connect xcframework to XCode project.

   • Option 1: via XCode GUI

     Open XCode project settings and add link to xcframework

   • Option 2: via Package.swift file

     // swift-tools-version:5.3 
     import PackageDescription
     
     let package = Package(
        name: "ExampleWithKotlinLibrary",
     
        products: [
           .library(
              name: "ExampleWithKotlinLibrary",
              targets: [
                 "ExampleWithKotlinLibrary",
                 "KotlinLibrary"
              ]
           )
        ],
     
        targets: [
           .target(
              name: "ExampleWithKotlinLibrary",
              dependencies: []
           ),
     
           .binaryTarget(
              name: "KotlinLibrary",
              path: "./xcframework/KotlinLibrary.xcframework"
           )
        ]
     )

---

Publish xcframework to Git

0. Complete 1-3 steps in section above.

1. Add credentials to local.properties file.

   git.credentials.username = USERNAME
   git.credentials.password = PASSWORD
   git.credentials.giturl = URL_TO_GIT_REPOSITORY.git

   NOTE: Do not forget to add this file to .gitignore.

2. Run publishXCFramework task to zip and publish it.

   ./gradlew publishXCFramework

3. Add binaryTarget in Package.swift file.

   let package = Package(
      // some code
      
      .binaryTarget(
         name: "KotlinLibrary",
         url: "pathToGitUrl",
         checksum: "..."
      )
   )

   NOTE: the binaryTarget name must match with name of the xcframework that is packed into the archive. By default, this is KotlinLibrary.

Samples

• Kotlin Multiplatform Mobile project using network libraries (AFNetworking for iOS, OkHttp for Android)
• Kotlin Multiplatform Project adding Kotlin library as XCFramework to Xcode project
• Kotlin Multiplatform Project for macOS target with Swift Package dependency

Contributing

Feel free to open an issue or submit a pull request for any bugs/improvements.