Injection

Injection is a tiny utility to help managing dependency injection.

Features:

• Singleton, dependencies that are only instantiated once and are shared amongst its users
• LazySingleton, dependencies that are only instantiated once, lazily, and are shared amongst its users
• Factory, dependencies that are instancied upon usage, unique to each user
• Utility property wrappers

Installation

Swift Package Manager

If you're working directly in a Package, add Injection to your Package.swift file

dependencies: [
    .package(url: "https://github.com/JARMourato/Injection.git", .upToNextMajor(from: "1.0.0" )),
]

If working in an Xcode project select File->Swift Packages->Add Package Dependency... and search for the package name: Injection or the git url:

https://github.com/JARMourato/Injection.git

Usage

1. Define dependencies:

import Injection

// A dependency that gets created every time it needs to be resolved, and therefore its lifetime is bounded to the instance that uses it
let reader = factory { RSSReader() }

// A dependency that gets created immediately and is shared throughout the lifetime of the application.
let database = singleton { Analytics() }

// A dependency that gets created only once, the first time it needs to be resolved and has the lifetime of the application.
let database = lazySingleton { Realm() }

// Syntatic sugar to combine dependencies to inject
let cacheModule = module {
    singleton { ImageCache() }
    factory { AudioCache() }
    factory { VideoCache() }
}

2. Inject the dependencies before the application is initialized:

import Injection

@main
class AppDelegate: UIResponder, UIApplicationDelegate {
    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        do {
            try inject {
                reader
                database
                cacheModule
            }
        } catch {
            print("TODO: Handle error properly... \(error)")
        }
        return true
    }
}

3. Use the injected dependencies using the provided property wrappers:

import Injection

class VideoPlayer: BackendProtocol {
    // Will resolve the dependency immediately upon type instantiation
    @Inject var database: Database
    
    // The dependency only gets resolved on the first time the property gets accessed
    @LazyInject var videoCache: VideoCache
    
    // The functionality is similar to `LazyInject` except the property may or may not have been injected.
    @OptionalInject var network: Network?
}

or via the initializer:

import Injection

struct Reader {
    private let rssReader: RSSReader
    
    init(rssReader: RSSReader = resolve()) {
        self.rssReader = rssReader
    }
}

Contributions

If you feel like something is missing or you want to add any new functionality, please open an issue requesting it and/or submit a pull request with passing tests 🙌

License

MIT

Contact

João (@_JARMourato)