在需要@Binding 的地方传递@Published 属性？

Question

当在 viewModel 中进行一些计算时，我想呈现模态视图。通常我需要为方法设置一些布尔绑定：

.fullScreenCover(isPresented: $isGalleryPresented) {
    GalleryPickerView())
}

where isGalleryPresented，是在视图中定义的@State。然而浏览SO，我发现我可以在viewModel中有属性：

@Pulished var isGalleryPresented = false

然后做这样的事情：

.fullScreenCover(isPresented: $viewModel.isGalleryPresented) {
    GalleryPickerView()
}

这很好用，虽然我不知道怎么做。 fullScreenCover 类型 isPresented: Binding<Bool> 的方法参数，我会尽我所能告诉发布者。这是如何工作的？

Answer 1

您的 viewModel 是 @ObservedObject 的包装属性，它通过键路径下标提供绑定到包装的可观察对象属性。

声明对应部分如下：

@available(iOS 13.0, macOS 10.15, tvOS 13.0, watchOS 6.0, *) @propertyWrapper @frozen public 
struct ObservedObject<ObjectType> : DynamicProperty where ObjectType : ObservableObject {

    /// A wrapper of the underlying observable object that can create bindings to
    /// its properties using dynamic member lookup.
    @dynamicMemberLookup @frozen public struct Wrapper {

        /// Returns a binding to the resulting value of a given key path.
        ///
        /// - Parameter keyPath  : A key path to a specific resulting value.
        ///
        /// - Returns: A new binding.
        public subscript<Subject>(dynamicMember keyPath: ReferenceWritableKeyPath<ObjectType, Subject>) -> Binding<Subject> { get }
    }

在需要@Binding 的地方传递@Published 属性？

Passing @Published property where @Binding is expected?

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