Service Locator Pattern with GameplayKit

ServiceLocator.swift

private class ServiceWrapper<T>: GKComponent {
    let service: T

    init(service: T) {
        self.service = service
        super.init()
    }

    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}

class ServiceLocator {
    private let registry = GKEntity()


    func register<T>(service: T) {
        registry.addComponent(ServiceWrapper(service: service))
    }

    func get<T>() -> T? {
        registry.component(ofType: ServiceWrapper<T>.self)?.service
    }

    var featureFlagService: FeatureFlagService? { return get() }
    var networkService: NetworkService? { return get() }
    var accessibilityService: AccessibilityService?  { return get() }
}

let SL = ServiceLocator()

SomeService.swift

class AccessibilityService {
    var isGrayscale: Bool {
        return UIAccessibility.shouldDifferentiateWithoutColor
    }
}

StartUp.swift

func registerServices() {
    SL.register(service: AccessibilityService())
}

Usage.swift

func getColor(hue: CGFloat) -> UIColor {
    let isGrayscale = SL.accessibilityService?.isGrayscale ?? false
    if isGrayscale {
        return UIColor(white: hue, alpha: 1.0)
    } else {
        return UIColor(hue: hue, saturation: 0.7, brightness: 0.8, alpha: 1.0)
    }
}