dmytro-anokhin

class Object {

    var anotherObject: AnotherObject
}

dmytro-anokhin

class Object {

    var children: [Object]
}

dmytro-anokhin

protocol Component {
    
    func foo()
}

class Composite: Component {
    
    var children: [Component] = []
    
    func foo() {

dmytro-anokhin

// Generated interface for UIView.h in Swift 4
extension UIView {

    open var subviews: [UIView] { get }
}

dmytro-anokhin

// Generated interface for UIViewController.h in Swift 4
extension UIViewController {

    @available(iOS 5.0, *)
    open var childViewControllers: [UIViewController] { get }
}

dmytro-anokhin

protocol Task {
  
    func run(_ completion: @escaping (_ task: Task) -> Void)
}

dmytro-anokhin

let tasks: [Task] = // List of concrete tasks

dmytro-anokhin

let group = DispatchGroup()

for task in tasks {
    group.enter()

    task.run({ task in
        group.leave()
    })
}

dmytro-anokhin

class CompositeTask: Task {
    
    let tasks: [Task]
    
    init(_ tasks: [Task]) {
        self.tasks = tasks
    }
    
    func run(_ completion: @escaping (Task) -> Void) {
        let group = DispatchGroup()

dmytro-anokhin

let compositeTask = CompositeTask(tasks)

compositeTask.run() { _ in
    print("All tasks completed")
}