使用 @Namespace 为 .matchedGeometryEffect 自定义初始化

Question

我正在尝试将带有 @Namespace 属性的自定义视图结构传递给 .matchedGeometryEffect 到 parent 视图。

由于 parent 将提供 Namespace 我正在使用自定义 init。

当我使用类似于 @Binding 自定义初始化的语法时，Xcode 强制我在初始化自定义视图时使用包装器。这反过来杀死了我的 .matchedGeometryEffect.

struct MyView<Content: View>: View {
    @Binding var matched: Bool
    @Namespace var nspace
    let content: Content
    
    init(matched: Binding<Bool>,
         nspace: Namespace,
         @ViewBuilder content: @escaping () -> Content
    ) {
        self._matched = matched
        self._nspace = nspace
        self.content = content()
    }
    
    var body: some View {
        ...
    }
}

似乎有效的是使用 var nspace: Namespace.ID 而不是 @Namespace var nspace 然后：

struct MyView<Content: View>: View {
    @Binding var matched: Bool
    var nspace: Namespace.ID
    let content: Content
    
    init(matched: Binding<Bool>,
         nspace: Namespace.ID,
         @ViewBuilder content: @escaping () -> Content
    ) {
        self._matched = matched
        self.nspace = nspace
        self.content = content()
    }
    
    var body: some View {
        ...
    }
}

这会不会在其他地方引起麻烦？有没有更好的方法？

Answer 1

Can this cause trouble somewhere else? Is there a better way?

它不是worse/better它是唯一正确的方法。让我们看看 API:

Namespace.ID是用来标识匹配效果命名空间的值

/// A dynamic property type that allows access to a namespace defined
/// by the persistent identity of the object containing the property
/// (e.g. a view).
@available(iOS 14.0, macOS 11.0, tvOS 14.0, watchOS 7.0, *)
@frozen @propertyWrapper public struct Namespace : DynamicProperty {

    @inlinable public init()

    public var wrappedValue: Namespace.ID { get }     // << here !!

正如所见

    ///   - namespace: The namespace in which defines the `id`. New
    ///     namespaces are created by adding an `@Namespace()` variable
    ///     to a ``View`` type and reading its value in the view's body
    ///     method.
    ///   - properties: The properties to copy from the source view.
    ///   - anchor: The relative location in the view used to produce
    ///     its shared position value.
    ///   - isSource: True if the view should be used as the source of
    ///     geometry for other views in the group.
    ///
    /// - Returns: A new view that defines an entry in the global
    ///   database of views synchronizing their geometry.
    ///
    @inlinable public func matchedGeometryEffect<ID>(id: ID, 
       in namespace: Namespace.ID,                             // << here !!
       properties: MatchedGeometryProperties = .frame, anchor: UnitPoint = .center, isSource: Bool = true) -> some View where ID : Hashable

使用 @Namespace 为 .matchedGeometryEffect 自定义初始化

Custom init with @Namespace for .matchedGeometryEffect

swift

xcode

swiftui

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