? 中介者(行为型模式)
用一个中介者对象封装一系列的对象交互，中介者使各对象不需要显示地相互作用，从而使耦合松散，而且可以独立地改变它们之间的交互。
示例：
protocol Receiver {
associatedtype MessageType
func receive(message: MessageType)
}
protocol Sender {
associatedtype MessageType
associatedtype ReceiverType: Receiver
var recipients: [ReceiverType] { get }
func send(message: MessageType)
}
struct Programmer: Receiver {
let name: String
init(name: String) {
self.name = name
}
func receive(message: String) {
print("\(name) received: \(message)")
}
}
final class MessageMediator: Sender {
internal var recipients: [Programmer] = []
func add(recipient: Programmer) {
recipients.append(recipient)
}
func send(message: String) {
for recipient in recipients {
recipient.receive(message: message)
}
}
}
用法
func spamMonster(message: String, worker: MessageMediator) {
worker.send(message: message)
}
let messagesMediator = MessageMediator()
let user0 = Programmer(name: "Linus Torvalds")
let user1 = Programmer(name: "Avadis 'Avie' Tevanian")
messagesMediator.add(recipient: user0)
messagesMediator.add(recipient: user1)
spamMonster(message: "I'd Like to Add you to My Professional Network", worker: messagesMediator)