ServiceLocator for iOS

The Service Locator is a design pattern used to decouple the way objects are obtained from the concrete classes that implement them. This is achieved by centralizing object creation to a single location, known as a service locator.

This tiny project has been inspired by RouterService and Swinject

Getting Started

1. Define Modules for Dependency Registration

Modules group related service registrations. They override the build() method to define how services should be registered with the locator.

class MyModule: ServiceLocatorModule {

    override func build() {

        // singletons
        single(ConfigProviderProtocol.self) {
            ConfigProvider()
        }

        // get dependencies with resolve
        single(URLFactory.self) {
            URLFactory(remoteConfigProvider: self.resolve())
        }

        // factory
        factory(AppLinkFactory.self) {
            let settingsManager: SettingsManager = self.resolve()

            return AppLinkFactory(descriptionFactory: settingsManager)
        }
    }
}

Tip: Define an application-wide module that includes other modules.

class AppModule: ServiceLocatorModule {

    override func build() {
        module { MyModule() }
    }
}

2. Initialize the Service Locator

lazy var myServiceLocator = startServiceLocator {
    AppModule()
}
myServiceLocator.build()

3. Retrieve dependency

3.1. In data structures

Retrieve dependencies in classes or structs using @Inject. The property wrapper automatically resolves the dependency from the service locator:

class MyCass {
    @Inject(myServiceLocator) public var contactSheet: ContactSheet
}

3.2 Local Variable Injection in Functions

For injecting dependencies within functions or methods, use @Inject before local variable declarations:

func doSomething() {
    @Inject(myServiceLocator) var contactSheet: ContactSheet
    // Use contactSheet here
}

3.3 Direct Resolution with resolve

If you prefer not using property wrappers, directly resolve dependencies using the service locator's resolve method:

let configProvider : ConfigProvider = serviceLocator.resolve()

4. Resetting the Service Locator

You can reset the ServiceLocator to its initial state, which can be useful in testing scenarios:

// Reset the entire service locator
resetServiceLocator(myServiceLocator)

// Or, if you have direct access to the ServiceLocator instance:
myServiceLocator.reset()

Tips and Customizations

Custom Property Wrapper

Create a tailored property wrapper if you have specific needs or want to simplify usage for a particular scope, like plugins in this example:

@propertyWrapper
internal final class PluginInject<T>: Dependency<T> {

    public var wrappedValue: T {
        resolvedWrappedValue()
    }

    public init() {
        super.init(MyPlugin.shared.myServiceLocator)
    }
}

Usage:

class MyClass {
    @PluginInject var contactSheet: ContactSheet
}

func doSomething() {
    @PluginInject var contactSheet: ContactSheet
}

Enabling Logging

You can enable logging for the ServiceLocator to help with debugging:

ServiceLocator.enableLogging = true

How to install

Swift Package Manager

Add the dependency to your Package.swift

    products: [
      ...
    ]
    dependencies: [
        .package(url: "https://github.com/kibotu/ServiceLocator", from: "1.0.2"),
    ],
    targets: [
      ...
    ]

Requirements

iOS 16.0 or later
Xcode 15.0 or later
Swift 5.10 or later

Contributions welcome!

License

Copyright 2024 Jan Rabe & CHECK24

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

   http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.