从OC到Swift(5)- 动态性,KVC\KVO

dynamic

  • 被@objc dynamic 修饰的内容会具有动态性,比如调用方法会走runtime那一套流程
class Dog: NSObject {
    @objc dynamic func test1() {}
    func test2() {}
}
var d = Dog()
d.test1()
d.test2()
  • 对应汇编
    从OC到Swift(5)- 动态性,KVC\KVO
    从OC到Swift(5)- 动态性,KVC\KVO

KVC\KVO

  • Swift支持KVC\KVO的条件
  • 属性所在的类、监听器最终继承自NSObject
  • 用@objc dynamic 修饰对应的属性
class Observer: NSObject {
    override func observeValue(forKeyPath keyPath: String?,
                               of object: Any?,
        change: [NSKeyValueChangeKey: Any]?,
        context: UnsafeMutableRawPointer?) {
        print("observeValue", change?[.newKey] as Any)
    }
}
class Person: NSObject {
    @objc dynamic var age: Int = 0
    var observer: Observer = Observer()
    override init() {
        super.init()
        self.addObserver(observer,
                         forKeyPath: "age",
                         options: .new,
                         context: nil)
    }
    deinit {
        self.removeObserver(observer,
                            forKeyPath: "age")
    }
}
var p = Person()
// observeValue Optional(20)
p.age = 20
// observeValue Optional(25)
p.setValue(25, forKey: "age")

block方式的KVO

class Person: NSObject {
    @objc dynamic var age: Int = 0
    var observation: NSKeyValueObservation?
    override init() {
        super.init()
        observation = observe(\Person.age, options: [.new, .old]) {
            (person, change) in
            print(change.newValue as Any)
        }
    }
}
var p = Person()
// Optional(20)
p.age = 20
// Optional(25)
p.setValue(25, forKey: "age")
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