为什么 associatedtype 不符合其约束协议中定义的协议？

Question

我正在尝试让我的 SwiftUI 视图更“可预览”，因此我正在使它们在其商店 (ViewModel) 上通用，这样我就可以更轻松地模拟它们。

考虑以下示例：

public protocol HomeViewStore: ObservableObject {
    associatedtype AnimatableImageStoreType = AnimatableImageStore

    var title: String { get }
    var animatableImageStores: [AnimatableImageStoreType] { get }
    var buttonTapSubject: PassthroughSubject<Void, Never> { get }
    var retryTapSubject: PassthroughSubject<Void, Never> { get }
}

public protocol AnimatableImageStore: ObservableObject, Identifiable {
    var imageConvertible: Data? { get }
    var onAppear: PassthroughSubject<Void, Never> { get }
}

struct AnimatableImage<
    AnimatableImageStoreType: AnimatableImageStore
>: View {
    @ObservedObject private var store: AnimatableImageStoreType

    public init(store: AnimatableImageStoreType) {
        self.store = store
    }

    ...
}

public struct HomeView<
    HomeViewStoreType: HomeViewStore
>: View {
    @StateObject private var store: HomeViewStoreType

    public init(store: HomeViewStoreType) {
        self._store = StateObject(wrappedValue: store)
    }

    public var body: some View {
        VStack {
            Text(store.title)
            Button {
                store.buttonTapSubject.send(())
            } label: {
                Text("API Call")
            }
            .background(Color(.accent))
            .padding()
            Button {
                store.retryTapSubject.send(())
            } label: {
                Text("Retry")
                    .font(.monserrat(.bold, 14))
            }
            .padding()
            List(store.animatableImageStores) { animatableImageStore in
                AnimatableImage(store: animatableImageStore)
            }
        }
        .background(Color(.accent))
    }
}

该代码给我以下错误消息：

我的问题是，为什么 HomeViewStoreType.AnimatableImageStoreType 在 HomeViewStore 协议中不符合 AnimatableImageStore 协议，我将其限制为 AnimatableImageStore 协议，而 AnimatableImageStore 符合的 Identifiable 也是如此？

如果有人能告诉我实现此目标的正确方法，我将不胜感激:)

Answer 1

此行不将 AnimatableImageStoreType 约束为 AnimatableImageStore:

associatedtype AnimatableImageStoreType = AnimatableImageStore

将 = 替换为 : 即可：

associatedtype AnimatableImageStoreType: AnimatableImageStore

为什么 associatedtype 不符合其约束协议中定义的协议？

Why does associatedtype not conform to protocols defined in its constraining protocol?

generics

ios

associated-types

swift

swift-protocols