英文:
SwiftUI: Initialize @StateObject with binding
问题
在我的 init() 中，我试图通过传递到作用域中的另一个变量的绑定来初始化一个 @StateObject 变量。
我想实现类似这样的效果：
struct MyView: View {
@State var value: Bool
@StateObject var viewModel: ViewModel
init() {
self.value = false
self.viewModel = ViewModel($value)
}
}
我知道通常在初始化过程中需要属性时，我们可以简单地创建它们的副本并在初始化程序中使用副本。然而，由于我试图使用绑定，绑定到变量的副本是行不通的。
我该如何实现这一目标？谢谢！
英文:
In my init(), I'm trying to initialize a @StateObject variable by passing in a binding to another variable in scope.
I want to achieve something like this:
struct MyView: View {
@State var value: Bool
@StateObject var viewModel: ViewModel
init() {
self.value = false
self.viewModel = ViewModel($value)
}
}
I know that when properties are needed during initialization normally, we can just create a copy of them and use the copy in the initializer. However, since I'm trying to use a binding, binding to a copy of a variable won't work.
How can I achieve this? Thank you!
答案1
得分: 1
如果value已经与视图模型绑定，更好的做法是在视图模型中声明它为@Published属性。
class ViewModel : ObservableObject {
@Published var value = false
}
struct MyView: View {
@StateObject var viewModel = ViewModel()
var body: some View {
Toggle("切换某事", isOn: $viewModel.value)
}
}
英文:
If value is bound to the view model anyway a better practice is to declare it in the view model as @Published property
class ViewModel : ObservableObject {
@Published var value = false
}
struct MyView: View {
@StateObject var viewModel = ViewModel()
var body: some View {
Toggle("Switch something", isOn: $viewModel.value)
}
}
答案2
得分: 0
这会有帮助吗？使用此方法，您可以将属性值存储在 ViewModel 内部，然后稍后可以像 $viewModel.value 这样使用该值。
struct MyView: View {
@StateObject private var viewModel: ViewModel
init() {
_viewModel = StateObject(wrappedValue: ViewModel(value: false))
}
}
英文:
Will this help?
With this, you can store the property value inside of the ViewModel and then you can use the value later with something like $viewModel.value.
struct MyView: View {
@StateObject private var viewModel: ViewModel
init() {
_viewModel = StateObject(wrappedValue: ViewModel(value: false))
}
}
答案3
得分: 0
chuan322的回答是一个好回答，但你可以稍作修改如下：
结构体 MyView: View {
@State var value: Bool
@StateObject var viewModel: ViewModel
init(value: Bool) {
self.value = value
_viewModel = StateObject(wrappedValue: ViewModel(value: value))
}
}
英文:
chuan322's answer is a good answer but you can revise it a little as below:
struct MyView: View {
@State var value: Bool
@StateObject var viewModel: ViewModel
init(value: Bool) {
self.value = value
_viewModel = StateObject(wrappedValue: ViewModel(value: value))
}
}
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