SwiftUI学习之state和Binding的区别浅析

来源：jb51　　时间：2021/3/29 8:51:08　　对本文有异议

@state 绑定值的状态,其属性的修饰官方推荐使用private.上代码(ps:这里没用private 进行修饰,是为了演示区别)
import SwiftUI

struct FilterView: View {
// @Binding var isFavorite: Bool
 @State var isFavorite = true
 
 var body: some View {
  Toggle(isOn: $isFavorite) {
   
  }
  let buttonTitle = isFavorite ? "呕吼" : "顿顿"
  Text(buttonTitle)
  
 }
}
struct ProductView: View {
 var titleS: String
 
 //:不想让外部访问的变量 需要初始化
 @State private var changeButtonTtile = true
 var body: some View {
  Button (action: {
   changeButtonTtile.toggle()
  }) {
   let buttonTitle = changeButtonTtile ? "哈哈哈" : "啦啦啦啦"
   Text(buttonTitle)
   FilterView(isFavorite: changeButtonTtile)
 
  }
 }
}

这里我们看到 @State var isFavorite = true通过state 进行修饰.这个时候我们点击FilterView的开关我们只能刷新当前FilterView的界面.注意这里:FilterView(isFavorite: changeButtonTtile) 初始化传入的是changeButtonTtile的value,也就实际值.

下面我们把State注释掉 ,打开@Bingding 那一行

import SwiftUI
 
struct FilterView: View {
 @Binding var isFavorite: Bool
// @State var isFavorite = true
 
 var body: some View {
  Toggle(isOn: $isFavorite) {
   
  }
  let buttonTitle = isFavorite ? "呕吼" : "顿顿"
  Text(buttonTitle)
  
 }
}
struct ProductView: View {
 var titleS: String
 
 //:不想让外部访问的变量 需要初始化
 @State private var changeButtonTtile = true
 var body: some View {
  Button (action: {
   changeButtonTtile.toggle()
  }) {
   let buttonTitle = changeButtonTtile ? "哈哈哈" : "啦啦啦啦"
   Text(buttonTitle)
   FilterView(isFavorite: $changeButtonTtile)
//:注意这里的取值 变成了$
  }
 }
}