How would you implement your own Dependency Injection mechanism for managing dependencies in an application?

To implement your own Dependency Injection (DI) mechanism in an iOS app, you can create a simple container that stores dependencies and provides them upon request.

Example in Swift:

// Protocol for a service
protocol ApiService {
    func fetchData()
}

// Concrete implementation
class ApiServiceImpl: ApiService {
    func fetchData() {
        print("Data loaded")
    }
}

// DI container
class DIContainer {
    static let shared = DIContainer()
    private var services = [String: Any]()

    func register<T>(_ service: T) {
        let key = String(describing: T.self)
        services[key] = service
    }

    func resolve<T>() -> T? {
        let key = String(describing: T.self)
        return services[key] as? T
    }
}

// Usage
let container = DIContainer.shared
container.register(ApiServiceImpl() as ApiService)

if let apiService: ApiService = container.resolve() {
    apiService.fetchData()
}

This approach allows centralized management of dependencies, simplifies testing, and increases code modularity.