[英]Optional @ObservableObject in SwiftUI
我想在 SwiftUI 中有一個可選的@ObservedObject,但我不斷收到編譯時錯誤。
Property type 'AModel?' does not match that of the 'wrappedValue' property of its wrapper type 'ObservedObject'
這是一些最小的可重現代碼。
import SwiftUI
public struct AView: View {
//MARK: View Model
//Error thrown here.
@ObservedObject var model: AModel?
//MARK: Body
public var body: some View {
Text("\(model?.value ?? 0)")
}
//MARK: Init
public init() {
}
}
class AModel: ObservableObject {
let value: Int = 0
}
技術原因是Optional
不是 class,所以它不能符合ObservableObject
。
但是,如果您想避免重構 object 本身 - 例如,如果它不在您的控制范圍內 - 您可以執行以下操作:
struct AView: View {
private struct Content: View {
@ObservedObject var model: AModel
var body: some View {
Text("\(model.value)")
}
}
var model: AModel?
var body: some View {
if let model = model {
Content(model: model)
} else {
Text("0")
}
}
}
您實際上希望您的init
參數是optional ,而不是 struct 屬性。 在你的情況下,我會簡單地做:
import SwiftUI
public struct AView: View {
//MARK: View Model
@ObservedObject var model: AModel
//MARK: Body
public var body: some View {
Text("\(model.value)")
}
//MARK: Init
public init(model: AModel? = nil) {
self.model = model ?? AModel()
}
}
class AModel: ObservableObject {
let value: Int = 0
}
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