App Dependencies

A simple - yet powerful - Dependency Injection library for Swift.

Heavily inspired by Factory and Dependencies.

Install

Add this package as a dependency to your Package.swift or the Package List in Xcode.

dependencies: [
    .package(url: "https://github.com/thomsmed/app-dependencies-swift.git", .branch: "main)
]

Add the AppDependencies product of this package as a product dependency to your targets.

dependencies: [
    .product(name: "AppDependencies", package: "AppDependenciesSwift")
]

Declare

By extending AppDependencies:

extension AppDependencies {
    var dependencyOne: Registration<DependencyOneProtocol> {
        Registration(self) { _ in
            DependencyOneVariantOne()
        }
    }

    var dependencyTwo: Registration<DependencyTwoProtocol> {
        Registration(self) { _ in
            DependencyTwoVariantOne()
        }
    }

    var dependencyThree: Registration<DependencyThreeProtocol> {
        Registration(self) {
            DependencyThree(
                dependencyOne: $0.dependencyOne(),
                dependencyTwo: $0.dependencyTwo()
            )
        }
    }
}

Resolve

By accessing the shared AppDependencies instance explicitly:

let dependencyOne = AppDependencies.shared.dependencyOne()
let dependencyThree = AppDependencies.shared.dependencyThree()
let dependencyTwo = AppDependencies.shared.dependencyTwo()

Using a property wrapper (which implicitly access the shared AppDependencies instance):

struct Model {
    @AppDependency(\.dependencyTwo) var dependencyTwo
    @AppDependency(\.dependencyThree) var dependencyThree
    @AppDependency(\.dependencyOne) var dependencyOne
}

Check out AppDependency for the various property wrapper alternatives.

Mock

Using a scoped (Task-Local stored) AppDependencies instance:

AppDependencies.scoped {
    $0.dependencyOne.use { _ in
        MockDependencyOne()
    }

    $0.dependencyTwo.use { _ in
        MockDependencyTwo()
    }

    let dependencyOne = AppDependencies.shared.dependencyOne()
    let dependencyThree = AppDependencies.shared.dependencyThree()
    let dependencyTwo = AppDependencies.shared.dependencyTwo()

    // ...

    #expect(dependencyOne is MockDependencyOne)
    #expect(dependencyTwo is MockDependencyTwo)
}

Using a scoped (Task-Local stored) AppDependencies instance (via property wrappers):

struct Model {
    @AppDependency(\.dependencyTwo) var dependencyTwo
    @AppDependency(\.dependencyThree) var dependencyThree
    @AppDependency(\.dependencyOne) var dependencyOne
}

AppDependencies.scoped {
    $0.dependencyOne.use { _ in
        MockDependencyOne()
    }

    $0.dependencyTwo.use { _ in
        MockDependencyTwo()
    }

    let model = Model()

    // ...

    #expect(model.dependencyOne is MockDependencyOne)
    #expect(model.dependencyTwo is MockDependencyTwo)
}

Using a scoped (Task-Local stored) AppDependencies instance during Unit/Model instantiation:

struct Model {
    @AppDependency(\.dependencyTwo) var dependencyTwo
    @AppDependency(\.dependencyThree) var dependencyThree
    @AppDependency(\.dependencyOne) var dependencyOne
}

let model = AppDependencies.scoped {
    $0.dependencyOne.use { _ in
        MockDependencyOne()
    }

    $0.dependencyTwo.use { _ in
        MockDependencyTwo()
    }

    return Model()
}

// ...

#expect(model.dependencyOne is MockDependencyOne)
#expect(model.dependencyTwo is MockDependencyTwo)

Disclaimer

This library is currently in an early experimentation phase, and might change drastically in all kind of ways. Use it more as a source of inspiration than anything else.

It is also heavily inspired by Factory and Dependencies, so definitely check out those!

License

MIT License

Copyright (c) 2025 Thomas Asheim Smedmann

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.