问题描述
我期望发生的事情:
单击该按钮后,工作表应显示一个随机数 (text
)。
会发生什么:第一次,工作表显示 foo
。在随后的时间里,会出现一个数字。
为什么第一次没有出现数字?
ContentView.swift
import SwiftUI
struct ContentView: View {
@State var showSheet = false
@State var text = "foo"
var body: some View {
vstack {
Text("Hello")
PillButton(title: "Start Test",action: {
print("Button tapped")
},text: $text,showSheet: $showSheet)
}.sheet(isPresented: $showSheet,content: {
Text(text)
})
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}
PillButton.swift
import SwiftUI
struct PillButton: UIViewRepresentable {
let title: String
let action: () -> ()
@Binding var text: String
@Binding var showSheet: Bool
var pillButton = UIButton()
func makeCoordinator() -> Coordinator { Coordinator(self) }
class Coordinator: NSObject {
var parent: PillButton
init(_ pillButton: PillButton) {
self.parent = pillButton
super.init()
}
@objc func doAction(_ sender: Any) {
let number = Int.random(in: 0..<100)
self.parent.text = String(number)
self.parent.action()
self.parent.showSheet = true
}
}
func makeUIView(context: Context) -> UIButton {
let button = UIButton(type: .system)
button.setTitle(self.title,for: .normal)
button.addTarget(context.coordinator,action: #selector(Coordinator.doAction(_ :)),for: .touchDown)
return button
}
func updateUIView(_ uiView: UIButton,context: Context) {}
}
解决方法
使用 ViewModel (ObservableObject) 类。在您的情况下 struct view 捕获了初始值。所以使用 ObservableObject 类来引用该值。
这是可能的解决方案。
class ContentViewModel: ObservableObject{
@Published var text = "foo"
}
struct ContentView: View {
@State var showSheet = false
@ObservedObject var viewModel = ContentViewModel()
var body: some View {
VStack {
Text("Hello")
PillButton(title: "Start Test",action: {
print("Button tapped")
},text: $viewModel.text,showSheet: $showSheet)
}.sheet(isPresented: $showSheet,content: {
Text(self.viewModel.text)
})
}
}