[英]SwiftUI: Data sharing between separate views
在视图之间共享变量的最佳做法是什么? 我的应用程序只有一个视图。 但是随着它变得越来越复杂,我认为我应该将它分成几个视图。 还要分开方法。 我从这样的事情开始:
struct ContentView: View {
@State var str: String = "String"
var body: some View {
VStack(alignment: .leading) {
Text(str)
TextField("Input", text: $str)
Button("button", action: { doSomething() })
}.padding()
}
func doSomething() {
str = str + " " + str
}
}
并想 go 那里:
class GlobalVars: ObservableObject {
@Published var str: String = "Initial String"
}
struct ContentView: View {
@ObservedObject var globalvars = GlobalVars()
var body: some View {
VStack(alignment: .leading) {
DisplayView()
EditView()
ControlView()
}.padding()
}
}
struct DisplayView: View {
@Binding var str: String
var body: some View {
Text(self.globalvars.str)
}
}
struct EditView: View {
@Binding var str: String
var body: some View {
TextField("Input", text: self.$str)
}
}
struct ControlView: View {
@Binding var str: String
var body: some View {
Button("button", action: { doSomething() })
}
}
func doSomething() {
@Binding var str: String
self.str = self.str + " " + self.str
}
我尝试使用@Published、@ObservedObject 和@Binding。 但不明白。 感谢您提前提供任何指示。
有很多方法可以解决这个问题。
我的选择可能是将绑定仅传递给您需要访问的变量。 这可能看起来像这样:
class GlobalVars: ObservableObject {
@Published var str: String = "Initial String"
}
struct ContentView: View {
@ObservedObject var globalvars = GlobalVars()
var body: some View {
VStack(alignment: .leading) {
DisplayView(str: globalvars.str) //don't need a binding here since it doesn't get modified
EditView(str: $globalvars.str)
ControlView(str: $globalvars.str)
}.padding()
}
}
struct DisplayView: View {
var str: String //don't need a binding here since it doesn't get modified
var body: some View {
Text(str)
}
}
struct EditView: View {
@Binding var str: String
var body: some View {
TextField("Input", text: $str)
}
}
struct ControlView: View {
@Binding var str: String
var body: some View {
Button("button", action: { doSomething() })
}
func doSomething() {
str = str + " " + str
}
}
请注意,现在在ContentView
中,有一个参数传递给每个子视图,其中包含到GlobalVars
str
属性的绑定(使用$
符号)。
此外, doSomething
被移入ControlView
的主体
您也可以使用 EnvironmentObject 来处理这个问题。 我个人不太喜欢这种方法,因为我宁愿明确地看到我的参数的去向。 它还使子视图可以访问整个 ObservableObject,这并不是必需的。 但是,它向您展示了校长:
class GlobalVars: ObservableObject {
@Published var str: String = "Initial String"
}
struct ContentView: View {
@ObservedObject var globalvars = GlobalVars()
var body: some View {
VStack(alignment: .leading) {
DisplayView()
EditView()
ControlView()
}.padding()
.environmentObject(globalvars)
}
}
struct DisplayView: View {
@EnvironmentObject var globalvars : GlobalVars
var body: some View {
Text(globalvars.str)
}
}
struct EditView: View {
@EnvironmentObject var globalvars : GlobalVars
var body: some View {
TextField("Input", text: $globalvars.str)
}
}
struct ControlView: View {
@EnvironmentObject var globalvars : GlobalVars
var body: some View {
Button("button", action: { doSomething() })
}
func doSomething() {
globalvars.str = globalvars.str + " " + globalvars.str
}
}
请注意,现在, globalvars
通过放置在具有.environmentObject
的视图层次结构中传递给子项。 每个子视图都可以通过声明@EnvironmentObject var globalvars: GlobalVars
您还可以做一种混合 model ,其中您将 ObservableObject 作为参数显式传递给子视图:
struct ContentView: View {
@ObservedObject var globalvars = GlobalVars()
var body: some View {
VStack(alignment: .leading) {
DisplayView(globalvars: globalvars)
}.padding()
.environmentObject(globalvars)
}
}
struct DisplayView: View {
@ObservedObject var globalvars : GlobalVars
var body: some View {
Text(globalvars.str)
}
}
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