Swiftpack.co - Package - bitwit/Slurp

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A Swift task runner and file watcher with an interface inspired by Gulp.js. Run it from your command line or inside of Xcode


Intended Uses

For automating workflows

Build your Slurp Task module as an executable. Run it from your CI server, the command line or Xcode. For example, this code builds and deploys an iOS app to the iTunes App Store:

import Slurp
import SlurpXCTools

let xcBuildConfig = XcodeBuild.Config(...)
let uploadConfig = ApplicationLoader.Config(...)
let slurp = Slurp()
    .register("buildAndDeploy") {
        return slurp
            |> Pod.Install()
            |> Version(.incrementBuildNumber, all: true)
            |> Version(.setMarketingVersion("1.0.1"), all: true)
            |> XcodeBuild([.archive, .export], config: xcBuildConfig)
            |> ApplicationLoader(.uploadApp, config: uploadConfig)

try! slurp.runAndExit(taskName: "buildAndDeploy")

Monitoring the filesystem for changes, then running tasks

This is useful for development workflows that involve files generated from 3rd party tools (e.g. graphics editors). If you are looking for ways to develop in Swift without using Xcode, this may be useful for running tests and linters automatically also.

import Slurp

let slurp = Slurp()
slurp.watch(paths: ["Tests/**.swift"], recursive: true)
.flatMap { _ in
  return try! slurp.run(taskName: "runTests")
.subscribe(onError: { err in

RunLoop.main.run() // Keep the task running indefinitely


Add Slurp to your package.swift and create a new executable Tasks module with Slurp as a dependency. You may also need SlurpXCTools for Xcode related Tasks. A basic package.swift might look like this:

import PackageDescription

let package = Package(
    name: "MyApp",
    products: [],
    dependencies: [
      .package(url: "https://github.com/bitwit/Slurp.git", .exact(.init(0, 0, 1))),
    targets: [
            name: "Tasks",
            dependencies: ["Slurp", "SlurpXCTools"])

A basic Sources/Tasks/main.swift file would look like:

import Slurp

let slurp = Slurp()

slurp.register("sayHello", Shell(arguments: ["echo", "hello world"]))

try! slurp.runAndExit(taskName: "sayHello")

From the command line you can now execute:

$ swift run Tasks

Developing and Running in Xcode

Start by setting up a workspace. Then run

$ swift package generate-xcodeproj --output myTasks.xcodeproj

Note: By default the xcodeproj file name is your Package name i.e. "MyApp.xcodeproj". Keep this generated xcodeproj separate from your main XCode target app so that can can rerun this command if necessary

Include this xcodeproj in your workspace. There should now be a scheme you can run to execute your task. You may need set your current working directory in order for this to run processes from the right folder.

Slurp.currentWorkingDirectory = "/path/to/app"

Note: You can pass this as an environment variable too through SLURP_CWD. This can be set in your task scheme's configuration

This git repo contains an xcworkspace and example app that mimic this suggested structure.

Currently Available Tasks

  • Shell
  • Xcodebuild (xcodebuild)
  • Version (agvtool)
  • ApplicationLoader (altool)
  • Cocoapods (pod)

Writing your own task

There are 3 ways to build your own task:

  1. Simply register an RxSwift Observable

    let myTaskObservable: Observable<Int> = Observable.create { observer in
    	return Disposables.create()
    .register("myTask") {
        return myTaskObservable
  2. Use the BasicTask class either directly or through inheritance. It can be initialized with either an RxSwift Observable or a callback function with a (Error?, T?) -> Void method signature

    open class BasicTask<T>: SlurpTask {
      public init(observable: Observable<T>)
      public convenience init(asyncTask: @escaping ( (Error?, T?) -> Void ) -> Void) 
  3. Make your class conform to the SlurpTask protocol:

    public protocol SlurpTask {
        associatedtype OutputType
        func onPipe<U>(from input: U) -> Observable<OutputType>

Note: onPipe<U>'s generic format is mostly there for posterity since all current tasks do not consume from the previous task's output. This may change in the future, particularly for file system management tasks

Options 2 & 3, which involve conforming to SlurpTask, are eligible for piping to and from other tasks.

The Pipe Operator

For convenience and cleanliness Slurp uses the pipe operator i.e |>. This is a substitute for calling func pipe(to: SlurpTask).

return slurp
            |> XcodeBuild([.archive, .export], config: xcBuildConfig)
            |> ApplicationLoader(.uploadApp, config: uploadConfig)

Is equivalent to

return slurp
            .pipe(to: XcodeBuild([.archive, .export], config: xcBuildConfig))
            .pipe(to: ApplicationLoader(.uploadApp, config: uploadConfig))


Some future desires/plans. Requests and contributions very welcome!

  • Solidify API
  • Slurp CLI
  • Dry run flag
  • Prettier output
  • Improve Xcode integration flow
  • Make more tasks. Personal wish list:
    • Swiftlint task
    • Slack API task
    • File system tasks
    • AWS S3 Management
    • AWS Cloudfront
    • Download Dsyms
    • Upload Dsyms to New Relic (and others)


Feel free to open an issue or find me on twitter


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0.0.1 - Mar 4, 2018