1. Concept
Decorator Pattern (Decorator): Dynamically add some additional responsibilities to an object. To extend the functionality of an object, decorators provide a more flexible alternative to inheritance.
More composition, less inheritance
Second, UML diagram
Abstract component class (Component): Gives an abstract interface to standardize objects that are ready to receive additional responsibilities
Concrete component class (ConcreteComponent): Define a specific class that is ready to accept additional responsibilities, which must implement the Component interface.
Decorator: Holds an instance of a Component object and defines an interface consistent with the abstract component.
Concrete Decoratator: Defines additional responsibilities for "sticking" to component objects.
Three, use cases
protocol Component {
func display() -> Void;
}
class ComponentDecorator: Component {
var component: Component
var border: String?
init(component: Component) {
self.component = component
}
func display() {
component.display()
}
}
class ListView: Component {
var name: String = "listView"
func display() {
print(name)
}
}
class BoxView: Component {
var name: String = "boxView"
func display() {
print(name)
}
}
class BlackBoder: ComponentDecorator {
override init(component: Component) {
super.init(component: component)
border = "black"
}
override func display() {
setBorder()
super.display()
}
func setBorder () {
print("this border is \(border ?? "default")")
}
}
class YellowBoder: ComponentDecorator {
override init(component: Component) {
super.init(component: component)
border = "yellow"
}
override func display() {
setBorder()
super.display()
}
func setBorder () {
print("this border is \(border ?? "default")")
}
}
user terminal:
class ViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
let component = ListView()
let componentB = YellowBoder(component: component)
componentB.display()
}
}