You don't need to ViewController anymore
Toggle、TextField、Slider都已经定义了Binding来绑定数据
introducing Combine and Advances in Foundation
Combine in Practice
//All In WWDC 2019
BindableObject Protocol
External
Reference type
Great for model you already have
class PodcastPlayerStore : BindableObject {
//Publisher
var didChange = PassthroughSubject<Void, Never>()
//...
func advance() {
currentEpisode = nextEpisode
currentTime = 0.0
// Notify subscribers that the player changed
didChange.send()
}
}
使用例子
Creating Dependencies on BindableObject
Pass directly with @ObjectBinding
Automatic dependency tracking
struct MyView : View {
@ObjectBinding var model: MyModelObject
...
}
//创建对象,绑定model
MyView(model: modelInstance)
struct PlayerView : View {
@EnvironmentObject var player: PodcastPlayerStore
var body: some View {
VStack {
Text(player.currentEpisode.title)
.foregroundColor(isPlaying ? .white : .gray)
Text(player.currentEpisode.showTitle)
.font(.caption).foregroundColor(.gray)
PlayButton(isPlaying: $player.isPlaying)
Text("\(player.currentTime, formatter: playheadTimeFormatter)")
}
}
}
Environment
Data applicable to an entire hierarchy
Convenience for indirection
Accent color, right-to-left, and more
Building Reusable Components
Read-only: Swift property, Environment
Read-write:@Binding
Prefer immutable access
@Binding
First class reference to data
*@Binding read and write a value without owning it
Great for reusability
Use $ to derive from source
Using State Effectively
Limit use if possible
Use derived Binding or value
Prefer BindableObject for persistence
Example: Button highlighting
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