Install Skip by running the Terminal command:
brew install skiptools/skip/skip
This will download and install the
skip tool itself, as well as the
gradle and JDK dependencies that are necessary for building and testing the Kotlin/Android side of your apps.
Ensure that the development prerequisites are satisfied by running:
If the checkup fails, check the FAQ for common solutions.
Once the checkup passes, you’re ready to start developing with Skip!
For closed-source commercial app development, Skip requires a license key, which will need the host id of the development machine, as shown by the command:
Enter this host identifier into the form at skip.tools/eval to receive an evaluation key that activates Skip for commercial development.
Creating an App
Create a new app project with the command:
skip init --open-xcode --appid=bundle.id project-name AppName
skip init --open-xcode --appid=com.xyz.HelloSkip hello-skip HelloSkip
This will create a
hello-skip/ folder with a new SwiftPM package containing a single module named
HelloSkip, along with folders named
Android and the shared
Skip.env app configuration file. The
Darwin folder will contain a
HelloSkip.xcodeproj project with a
HelloSkip target, which can be opened in Xcode.
Xcode will open the new project, but before you can build and launch the transpiled app, an Android emulator needs to be running. Launch
Android Studio.app and open the
Virtual Device Manager from the ellipsis menu of the Welcome dialog. From there,
Create Device (e.g., “Pixel 6”) and then
Launch the emulator.
Once the Android emulator is running, select and run the
HelloSkip target in Xcode. The first build will take some time to compile the Skip libraries, and you may be prompted with a dialog to affirm that you trust the Skip plugin. Once the build and run action completes, the SwiftUI app will open in the selected iOS simulator, and at the same time the transpiled app will launch in the currently-running Android emulator.
Browse to the
ContentView.swift file and make a small change and re-run the target: the app will be re-built and re-run on both platforms simultaneously with your changes.
See the product documentation for further information developing with Skip. Happy Skipping!
Creating a Multi-Module App
Skip is designed to accommodate and encourage using multi-module projects. The default
skip init command creates a single-module app for simplicity, but you can create a modularized project by specifying additional module names at the end of the chain. For example:
skip init --open-xcode --appid=com.xyz.HelloSkip multi-project HelloSkip HelloModel HelloCore
This command will create a SwiftPM project with three modules:
HelloCore. The heuristics of such module creation is that the modules will all be dependent on their subsequent peer module, with the first module (
HelloSkip) having an initial dependency on
SkipUI, the second module depending on
SkipModel, and the final module in the chain depending on
Package.swift file can be manually edited to shuffle around dependencies, or to add new dependencies on external Skip frameworks such as the nascent SkipSQL or SkipXML libraries.
Creating a Dual-Platform Framework
Skip framework projects are pure SwiftPM packages that encapsulate common functionality. They are simpler than app projects, as they do not need
Each of the core Skip compatibility frameworks (skip-lib, skip-unit, skip-foundation, and skip-ui) are Skip framework projects. Other commonly-used projects include skip-sql, skip-script, and skip-zip.
A new framework project can be created and opened with:
skip init --build --test lib-name ModuleName
This will create a new
lib-name folder containing a
Package.swift with targets of
This project can be opened in Xcode.app, which you can use to build and run the unit tests. Running
swift build and
swift test from the Terminal can also be used for headless testing as part of a continuous integration process.
Skip Framework Structure
The structure of a Skip framework is exactly the same as any other SPM package:
lib-name ├── Package.resolved ├── Package.swift ├── README.md ├── Sources │ └── ModuleName │ ├── ModuleName.swift │ ├── Resources │ │ └── Localizable.xcstrings │ └── Skip │ └── skip.yml └── Tests └── ModuleNameTests ├── ModuleNameTests.swift ├── Resources │ └── TestData.json ├── Skip │ └── skip.yml └── XCSkipTests.swift
Skip frameworks use a standard
Package.swift file, with the exception of an added dependency on
skip and use of the
skipstone plugin for transpilation:
// swift-tools-version: 5.8 import PackageDescription let package = Package( name: "lib-name", defaultLocalization: "en", platforms: [.iOS(.v16), .macOS(.v13), .tvOS(.v16), .watchOS(.v9), .macCatalyst(.v16)], products: [ .library(name: "ModuleName", targets: ["ModuleName"]), ], dependencies: [ .package(url: "https://source.skip.tools/skip.git", from: "0.7.31"), .package(url: "https://source.skip.tools/skip-foundation.git", from: "0.0.0"), ], targets: [ .target(name: "ModuleName", plugins: [.plugin(name: "skipstone", package: "skip")]), .testTarget(name: "ModuleNameTests", dependencies: ["ModuleName"], plugins: [.plugin(name: "skipstone", package: "skip")]), ] )
skip init Reference
zap /tmp % skip init --help OVERVIEW: Initialize a new Skip project USAGE: skip init [<options>] <project-name> <module-names> ... ARGUMENTS: <project-name> Project folder name <module-names> The module name(s) to create OUTPUT OPTIONS: -o, --output <path> Send output to the given file (stdout: -) -E, --message-errout Emit messages to the output rather than stderr -v, --verbose Whether to display verbose messages -q, --quiet Quiet mode: suppress output -J, --json Emit output as formatted JSON -j, --json-compact Emit output as compact JSON -M, --message-plain Show console messages as plain text rather than JSON -A, --json-array Wrap and delimit JSON output as an array --plain/--no-plain Show no colors or progress animations (default: --no-plain) CREATE OPTIONS: --id <id> Application identifier (default: net.example.MyApp) -d, --dir <directory> Base folder for project creation -c, --configuration <c> Configuration debug/release (default: debug) -t, --template <id> Template name/ID for new project (default: skipapp) -h, --template-host <host> The host name for the template repository (default: https://github.com) -f, --template-file <zip> A path to the template zip file to use --resource-path <resource-path> Resource folder name (default: Resources) --chain/--no-chain Create library dependencies between modules (default: --chain) --zero/--no-zero Add SKIP_ZERO environment check to Package.swift (default: --zero) --git-repo/--no-git-repo Create a local git repository for the app (default: --no-git-repo) --free Create package in free mode --show-tree/--no-show-tree Display a file system tree summary of the new files (default: --no-show-tree) --module-tests/--no-module-tests Whether to create test modules (default: --module-tests) --validate-package/--no-validate-package Validate generated Package.swift files (default: --validate-package) TOOL OPTIONS: --xcodebuild <path> Xcode command path --swift <path> Swift command path --gradle <path> Gradle command path --adb <path> ADB command path --emulator <path> Android emulator path --android-home <path> Path to the Android SDK (ANDROID_HOME) BUILD OPTIONS: --build/--no-build Run the project build (default: --build) --test/--no-test Run the project tests (default: --no-test) --verify/--no-verify Verify the project output (default: --verify) OPTIONS: --appid <appid> Embed the library as an app with the given bundle id --icon-color <RGB> RGB hexadecimal color for icon background (default: 4994EC) --version <version> Set the initial version to the given value --open-xcode Open the resulting Xcode project --open-gradle Open the resulting Gradle project -h, --help Show help information.
Skip’s architecture relies on recent advances in the plugin system used by Xcode 15 and Swift Package Manager 5.9. When unexpected issues arise, often the best first step is to clean your Xcode build (
Clean Build Folder) and reset packages (
Reset Package Caches). Restarting Xcode is sometimes warranted, and trashing the local
DerivedData/ folder might even be needed.
Xcode sometimes reports error messages like the following:
Internal inconsistency error (didStartTask): targetID (174) not found in _activeTargets. Internal inconsistency error (didEndTask): '12' missing from _activeTasks.
When these errors occur, the build appears to complete successfully although changes are not applied. Unfortunately, this is an Xcode bug. We have found the following workarounds:
- Continue to retry the build. Eventually Xcode may complete successfully, although the errors often continue to become more frequent until you are forced to apply one of the other solutions below.
- Building a different target and then re-building your app target may clear the error.
- Restart Xcode.
- Clean and rebuild.
You can read more about this Xcode error on the Swift.org forums.
Skip may highlight the wrong line in build errors. When Skip surfaces the wrong line number, it is typically only one line off.