KVO vs NSNotification vs 协议委托

KVO vs NSNotification vs 协议/委托

swift
class Person: NSObject {
    @objc dynamic var name: String
    
    init(name: String) {
        self.name = name
    }
}
class Observer: NSObject {
    var person: Person
    
    init(person: Person) {
        self.person = person
        super.init()
        
        person.addObserver(self, forKeyPath: "name", options: .new, context: nil)
    }
    
    override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
        if keyPath == "name" {
            if let newName = change?[.newKey] as? String {
                print("Person's name changed to \(newName)")
            }
        }
    }
    
    deinit {
        person.removeObserver(self, forKeyPath: "name")
    }
}
let person = Person(name: "John")
let observer = Observer(person: person)
person.name = "Tom" // 输出：Person's name changed to Tom

swift
class Sender {
    func sendMessage() {
        NotificationCenter.default.post(name: NSNotification.Name("MessageNotification"), object: self, userInfo: ["message": "Hello"])
    }
}
class Receiver {
    init() {
        NotificationCenter.default.addObserver(self, selector: #selector(handleMessage(_:)), name: NSNotification.Name("MessageNotification"), object: nil)
    }
    
    @objc func handleMessage(_ notification: Notification) {
        if let message = notification.userInfo?["message"] as? String {
            print("Received message: \(message)")
        }
    }
}
let sender = Sender()
let receiver = Receiver()
sender.sendMessage() // 输出：Received message: Hello

swift
protocol MessageDelegate: AnyObject {
    func didReceiveMessage(message: String)
}
class Sender {
    weak var delegate: MessageDelegate?
    
    func sendMessage() {
        delegate?.didReceiveMessage(message: "Hello")
    }
}
class Receiver: MessageDelegate {
    init() {
        let sender = Sender()
        sender.delegate = self
        sender.sendMessage()
    }
    
    func didReceiveMessage(message: String) {
        print("Received message: \(message)")
    }
}
let receiver = Receiver() // 输出：Received message: Hello