---
title: modern-swift-dev/skein-swift
framework: Swift Package Catalog
role: article
path: packages/modern-swift-dev/skein-swift
---

# modern-swift-dev/skein-swift

`Skein` is a small, type-safe dependency-injection container for Swift. Its default API is MainActor-isolated, with explicit Sendable nonisolated and custom-global-actor alternatives.

## Why Skein?

A skein is a length of thread gathered into a connected bundle. The name reflects how this library brings the individual threads of an application's dependency graph together into one explicit, inspectable composition.

## Install

Add `https://github.com/modern-swift-dev/skein-swift` as a package dependency in Xcode, or add it to a Swift Package Manager manifest:

```swift dependencies: [     .package(         url: "https://github.com/modern-swift-dev/skein-swift",         from: "1.0.1"     ) ] ```

Then depend on the `Skein` product:

```swift .product(name: "Skein", package: "skein-swift") ```

## Quick start

Bindings declare their exposed type and receive a `Resolver` for their own dependencies. A `single` is created once on first use; a `factory` creates a new value for every resolution.

```swift import Skein

protocol HTTPClient { } final class URLSessionClient: HTTPClient { }

final class UserService {     init(client: any HTTPClient) { } }

let appModule = module {     single((any HTTPClient).self, provider: { _ in URLSessionClient() })     factory(UserService.self, using: UserService.init) }

try startSkein {     appModule }

let service: UserService = try get() stopSkein() ```

All setup and resolution operations that can fail use Swift error handling, so call them with `try` and handle failures appropriate to your application.

## Documentation

The [central documentation repository](https://github.com/modern-swift-dev/docs) owns Astro, the shared theme, and website/API generation. It builds from `main` daily and on manual runs. Edit page Markdown in `Documentation/Site/` and keep DocC catalogs beside the module sources. See the [docs README](https://github.com/modern-swift-dev/docs/blob/main/README.md) for local build and preview commands. Do not commit generated HTML to this repository.

Start with the hosted guides:

- [Overview](https://modern-swift-dev.github.io/docs/skein-swift/) - [Documentation index](https://modern-swift-dev.github.io/docs/skein-swift/documentation/) - [Getting started](https://modern-swift-dev.github.io/docs/skein-swift/documentation/getting-started/) - [Examples](https://modern-swift-dev.github.io/docs/skein-swift/examples/)

The site publishes separate API references for each library product:

- [Skein API](https://modern-swift-dev.github.io/docs/skein-swift/api/skein/) - [SkeinSwiftUI API](https://modern-swift-dev.github.io/docs/skein-swift/api/skein-swiftui/)

Each stable GitHub release includes `Skein-Documentation.zip`, containing the two matching `.doccarchive` bundles. Download and unzip it, then open each bundle in Xcode to add it to the Documentation browser.

Build the same archive locally with:

```sh make documentation ```

## Runnable examples

The [`Examples`](Examples/README.md) package contains independent, executable use cases for:

- singleton and factory lifetimes; - dependency chains and module composition; - protocol-oriented registrations; - qualified bindings; - lifecycle and provider-error handling; - MainActor-first services, binding-owned roots, and async startup validation; - test isolation and hand-written fakes.

Run any example directly from the repository root:

```sh swift run --package-path Examples BasicUsage swift run --package-path Examples ModularComposition swift run --package-path Examples QualifiedBindings swift run --package-path Examples ErrorHandling swift run --package-path Examples MainActorValidation swift test --package-path Examples ```

These examples depend on the local checkout of Skein, so they also serve as compile-checked usage references while the API evolves.

## Contributing

See [CONTRIBUTING.md](CONTRIBUTING.md) for website development and release instructions.

## Package Metadata

Repository: modern-swift-dev/skein-swift

Default branch: main

README: README.md