Swift 以前是通过addObserver来实现对某个属性的变化监听,而最新的变化,书写起开更加方便。observer = test observe( fi
Swift 以前是通过addObserver
来实现对某个属性的变化监听,而最新的变化,书写起开更加方便。
observer = test.observe(\.field, options: [.new, .initial]) { (object, change) in print(change) }
一定要用属性赋值当前的 observe 结果,没有的话可能会造成 change 不生效。
对 UIScrollView 的滚动监听,我们可以使用UIScrollViewDelegate
extension UIScrollViewDelegate{ func scrollViewDidScroll(scrollView: UIScrollView){ //do something } }
这里推荐使用 Observe 比较方便的是可以进行模块的逻辑的拆分,我们只需在自己的组件里面进行监听
class ComponetView: UIVIew { private var observation: NSKeyValueObservation? init(targetView: UIView) { observation = targetView.observe(\.contentOffset, options: [.new]) { [weak self] scrollView, change in // handle data contentOffset } } }
附录:Swift中实现Observable机制
今天给别人讲个Observable的实现和使用场景,结合Observable-Swiftgithub:https://github.com/slazyk/Observable-Swift讲了半天貌似还没有特别明白,故写了个简易的实现,讲述了下Observable属性监控机制。
//: Playground - noun: a place where people can play import UIKit import Foundation // MARK: - Observable class Observable<T> { // 定义block结构 typealias Observer = T -> Void // 申明一个block,用于数据改变的执行 private var observer: Observer? // 数据发生变更,则通过observer告知 var value: T { didSet { observer?(value) } } init(_ v: T) { value = v } func observe(observer: Observer?) { self.observer = observer observer?(value) } } // MARK: - People struct PeopleModel { let firstName: Observable<String> let lastName: Observable<String> init(firstName: String, lastName: String) { self.firstName = Observable(firstName) self.lastName = Observable(lastName) } } // MARK: - Test // test1 let people = PeopleModel(firstName: "sunny", lastName: "liu") people.firstName.observe { newValue in print("firstName changed: \(newValue)") } people.lastName.observe { print("lastName changed: \($0)") } people.firstName.value = "sunny2" people.lastName.value = "liu2" // test2 class House { let lableHouseName = UILabel() init() { } var people: PeopleModel? { didSet { people?.firstName.observe{ [unowned self] in self.lableHouseName.text = $0 } } } }
这样貌似容易理解了,O(∩_∩)O哈哈~
总结
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