@objc class Person: NSObject {
    @objc dynamic var name:String?

    init(name: String) {
        self.name = name;

    }
    

       var person:Person!

       self.person = Person.init(name: "xiaoming")
        print("name:\(person.name)")//name:Optional("xiaoming")
        
        // 取值
        var value = self.person.value(forKey: "name") as? String //name:Optional("xiaoming")
        print("name:\(value)")//name:Optional("xiaoming")
        
        //使用
        self.person.setValue("xiaohua", forKeyPath: "name")
        print("name:\(person.name)")//name:Optional("xiaohua")
        
        //使用字典
        let dict = ["name":"小光"]
        self.person.setValuesForKeys(dict)
        let dictOut = self.person.dictionaryWithValues(forKeys: ["name"])
        print("\(dictOut)")//["name": 小光]

        self.person.name = "xiaoming"
        self.person.addObserver(self, forKeyPath: "name", options: NSKeyValueObservingOptions.new, context: nil)// 监听（KVO的属性必须设置dynamic）.addObserver(self, forKeyPath: "userName", options: NSKeyValueObservingOptions.new, context: nil)// 监听（KVO的属性必须设置dynamic）
        let deadline = DispatchTime.now() + 5.0
        DispatchQueue.global().asyncAfter(deadline: deadline) {
            self.person.name = "xiaoxiao"
        }

    override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
        if "name" == keyPath {
            
            print("之前的: \(String(describing: change?[.oldKey]))")//不知道为什么这里一直是nil
            
            if let newValue = change?[.newKey] {
                print("最新的: \(newValue)")//最新的: xiaoxiao
            }
        }
    }