swiftui - PresentationMode 触发“在初始化之前使用的变量 X”
问题描述
我正在尝试为 SwiftUI 应用程序编写一个可重用的快速选择字段编辑器。下面的代码仅在存在 时显示Variable 'self.fieldValue' used before initialized
错误@Environment(\.presentationMode) var presentationMode: Binding<PresentationMode>
。如果我删除它,视图编译得很好。任何人都知道为什么presentationmode环境变量会导致这个以及如何解决它?我需要presentationmode env var,因此一旦用户单击按钮,我就可以快速弹出视图。
@Environment(\.presentationMode) var presentationMode: Binding<PresentationMode>
@State var viewName = "Edit Field"
@Binding var fieldValue: Int
@State var fieldName: String = ""
var options: [Int]
init(title: String, field: String, value: Binding<Int>, list: [Int]) {
viewName = title
fieldName = field
_fieldValue = value
options = list
}
有关完整视图代码,请参见下文。
import SwiftUI
struct CommonNumberEditView: View {
@Environment(\.presentationMode) var presentationMode: Binding<PresentationMode>
@State var viewName = "Edit Field"
@Binding var fieldValue: Int
@State var fieldName: String = ""
var options: [Int]
init(title: String, field: String, value: Binding<Int>, list: [Int]) {
viewName = title
fieldName = field
_fieldValue = value
options = list
}
var body: some View {
ZStack {
Image("sky")
.resizable()
.frame(minWidth: 0, maxWidth: .infinity, minHeight: 0, maxHeight: .infinity)
.edgesIgnoringSafeArea(.all)
.opacity(0.5)
VStack(alignment: .center, spacing: 5)
{
JumpLogNumberField(label: self.fieldName, val: self.$fieldValue)
ScrollView {
VStack(alignment: .center, spacing: 5) {
ForEach(options, id: \.self) { item in
Group {
Button(action: {
self.presentationMode.wrappedValue.dismiss()
}) {
Text(String(item))
.foregroundColor(.black)
.padding(20)
}
.frame(minWidth:0, maxWidth: .infinity)
.background(Color.white.opacity(0.6))
}
}
}
}
.frame(minWidth: 0, maxWidth: .infinity, minHeight: 0, maxHeight: .infinity, alignment: .top)
}
.padding(.top, 40)
.padding(.leading, 40)
.padding(.trailing, 40)
.frame(minWidth: 0, maxWidth: .infinity, minHeight: 0, maxHeight: .infinity)
}.navigationBarTitle(viewName, displayMode: .inline)
}
}
struct CommonFieldEditView_Previews: PreviewProvider {
static var previews: some View {
CommonNumberEditView(title: "Edit Field", field: "Altitude", value: .constant(5000), list: [ 13500, 10000, 5500, 3500 ])
}
}
解决方案
这是代码的固定部分:
struct CommonNumberEditView: View {
@Environment(\.presentationMode) var presentationMode
@State private var viewName: String
@Binding var fieldValue: Int
@State private var fieldName: String
var options: [Int]
init(title: String, field: String, value: Binding<Int>, list: [Int]) {
_viewName = State(initialValue: title)
_fieldName = State(initialValue: field)
_fieldValue = value
options = list
}
// ...
使用 Xcode 13 / iOS 15 测试
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