Swiftpack.co - Package - ibm-functions/runtime-swift

IBM Cloud Functions runtime for swift

Build Status


Quick Swift Action

Simple swift action hello.swift

The traditional support for dictionary still works:

func main(args: [String:Any]) -> [String:Any] {
    if let name = args["name"] as? String {
        return [ "greeting" : "Hello \(name)!" ]
    } else {
        return [ "greeting" : "Hello swif4!" ]

Swift 4.x support

Some examples of using Codable In and Out

Codable style function signature

Create file helloCodableAsync.swift

// Domain model/entity
struct Employee: Codable {
  let id: Int?
  let name: String?
// codable main function
func main(input: Employee, respondWith: (Employee?, Error?) -> Void) -> Void {
    // For simplicity, just passing same Employee instance forward
    respondWith(input, nil)
wsk action update helloCodableAsync helloCodableAsync.swift swift:4.1

ok: updated action helloCodableAsync

wsk action invoke helloCodableAsync -r -p id 42 -p name Carlos
    "id": 42,
    "name": "Carlos"

Codable Error Handling

Create file helloCodableAsync.swift

struct Employee: Codable {
    let id: Int?
    let name: String?
enum VendingMachineError: Error {
    case invalidSelection
    case insufficientFunds(coinsNeeded: Int)
    case outOfStock
func main(input: Employee, respondWith: (Employee?, Error?) -> Void) -> Void {
    // Return real error
        throw VendingMachineError.insufficientFunds(coinsNeeded: 5)
    } catch {
        respondWith(nil, error)
wsk action update helloCodableError helloCodableError.swift swift:4.1

ok: updated action helloCodableError

wsk action invoke helloCodableError -b -p id 42 -p name Carlos
"name": "helloCodableError",
"response": {
  "result": {
    "error": "insufficientFunds(5)"
"status": "application error",
"success": false

Packaging an action as a Swift executable using Swift 4

When you create an OpenWhisk Swift action with a Swift source file, it has to be compiled into a binary before the action is run. Once done, subsequent calls to the action are much faster until the container holding your action is purged. This delay is known as the cold-start delay.

To avoid the cold-start delay, you can compile your Swift file into a binary and then upload to OpenWhisk in a zip file. As you need the OpenWhisk scaffolding, the easiest way to create the binary is to build it within the same environment as it will be run in. These are the steps:

  • Run an interactive Swift action container.

    docker run --rm -it -v "$(pwd):/owexec" ibmfunctions/action-swift-v4.1 bash

    This puts you in a bash shell within the Docker container.

  • Copy the source code and prepare to build it.

    cp /owexec/hello.swift /swift4Action/spm-build/Sources/Action/main.swift
    cat /swift4Action/epilogue.swift >> /swift4Action/spm-build/Sources/Action/main.swift
    echo '_run_main(mainFunction:main)' >> /swift4Action/spm-build/Sources/Action/main.swift

    Copy any additional source files to /swift4Action/spm-build/Sources/Action/

  • (Optional) Create the Package.swift file to add dependencies.

// swift-tools-version:4.0
// The swift-tools-version declares the minimum version of Swift required to build this package.

import PackageDescription

let package = Package(
    name: "Action",
    products: [
        name: "Action",
        targets:  ["Action"]
    dependencies: [
      .package(url: "https://github.com/IBM-Swift/SwiftyRequest.git", .upToNextMajor(from: "1.0.0"))
    targets: [
        name: "Action",
        dependencies: ["SwiftyRequest"],
        path: "."

As you can see this example adds SwiftyRequest dependencies.

Notice that now with swift:4.1 is no longer required to include CCurl, Kitura-net and SwiftyJSON in your own Package.swift. You are free now to use no dependencies, or add the combination that you want with the versions you want.

  • Copy Package.swift to spm-build directory

    cp /owexec/Package.swift /swift4Action/spm-build/Package.swift
  • Change to the spm-build directory.

    cd /swift4Action/spm-build
  • Compile your Swift Action.

    swift build -c release
  • Create the zip archive.

    zip /owexec/hello.zip .build/release/Action
  • Exit the Docker container.


    This has created hello.zip in the same directory as hello.swift.

  • Upload it to OpenWhisk with the action name helloSwifty:

    wsk action update helloSwiftly hello.zip ibmfunctions/action-swift-v4.1
  • To check how much faster it is, run

    wsk action invoke helloSwiftly --blocking

Migrating from Swift 3 to Swift 4

Helper compile.sh helper script

When compiling and packaging your swift 4 action, there are a couple of differences. All your source code needs to be copied to /swift4Action/spm-build/Sources/Action/ instead of /swift3Action/spm-build/ You Package.swift needs to have the first line with a comment indicating swift4 tooling and format

// swift-tools-version:4.0

For swift 4 you need specify additional information in Package.swift such as products with executable name Action and targets

You can take a look at the helper script tools/build/compile.sh to compile and zip your Actions. Having a project directory Hello under a directory actions like the following:


Change to the parent directory then run the compile script specify the project directory, the kind swift:3.1.1 or swift:4.1 and any swiftc build flags like the following:

cd actions/
incubator-runtime-swift/tools/build/compile.sh Hello swift:4.1 -v

This will produce a zip build/swift4/Hello.zip

SwiftyJSON using single source action file

If you have a swift:3.1.1 action not compile, just as source using the SwiftyJSON package, you need to precompile your action and specify the version of SwiftyJSON you wan to use for swift:4.1 kind action. Take into account that starting with Swift 4 there is better support to manage JSON data natively.

Note: This is only applicable to the base image provided for the Swift 4 runtime, other downstream such as IBM Cloud Functions extending this image might provide additional SDK and packages including SwiftyJSON and IBM Watson SDK, check the vendor documentation for more specific information about packages and versions.

To use on deployment that contains the rutime as a kind

To use as a kind action

wsk action update myAction myAction.swift --kind swift:4.1

Local development


Build all runtime images

./gradlew :swift4.1:distDocker

This will produce the image whisk/action-swift-v4.1 and whisk/action-swift-v4.1

Build and Push image

docker login
./gradlew :swift4.1:distDocker -PdockerImagePrefix=$prefix-user -PdockerRegistry=docker.io


Deploy OpenWhisk using ansible environment that contains the kind swift:4.1 Assuming you have OpenWhisk already deploy localy and OPENWHISK_HOME pointing to root directory of OpenWhisk core repository.

Set ROOTDIR to the root directory of this repository.

Redeploy OpenWhisk

cd $OPENWHISK_HOME/ansible
ANSIBLE_CMD="ansible-playbook -i ${ROOTDIR}/ansible/environments/local"
$ANSIBLE_CMD setup.yml
$ANSIBLE_CMD couchdb.yml
$ANSIBLE_CMD initdb.yml
$ANSIBLE_CMD wipe.yml
$ANSIBLE_CMD openwhisk.yml

Or you can use wskdev and create a soft link to the target ansible environment, for example:

ln -s ${ROOTDIR}/ansible/environments/local ${OPENWHISK_HOME}/ansible/environments/local-swift
wskdev fresh -t local-swift


Install dependencies from the root directory on $OPENWHISK_HOME repository

./gradlew :common:scala:install :core:controller:install :core:invoker:install :tests:install

Using gradle to run all tests

./gradlew :tests:test

Using gradle to run some tests

./gradlew :tests:test --tests *ActionContainerTests*

Using IntelliJ:

  • Import project as gradle project.
  • Make sure working directory is root of the project/repo

Using container image to test

To use as docker action push to your own dockerhub account

docker tag whisk/action-swift-v4.1 $user_prefix/action-swift-v4.1
docker push $user_prefix/action-swift-v4.1

Then create the action using your the image from dockerhub

wsk action update myAction myAction.swift --docker $user_prefix/action-swift-v4.1

The $user_prefix is usually your dockerhub user id.


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