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Swift 中监听属性值变化（观察者模式）

2022-07-20 22:23:00 【hello_Jesse】

很简单，直接上代码，一看就会

class Test3ViewController: BaseViewController {
    
    lazy var person:Person = {
    
      let p = Person()
      return p
    }()
    var observer:NSKeyValueObservation?
    override func viewDidLoad() {
    
        super.viewDidLoad()
        person.name  = "jack"
        observer = person.observe(\Person.name, options: [.old,.new], changeHandler: {
     person,change in
            if let old = change.oldValue {
    
                print("old == \(old)") //old == jack
            }
            if let new = change.newValue {
    
                print("new == \(new)")//new == rose
            }
        })
        person.name  = "rose"
    }
 }
 
class Person:NSObject {
    
    @objc dynamic var name = ""
}