swift - 如何让 Swift Coordinator 反射(reflect) parent 的绑定(bind)变化？

Question

假设我有:

• 结构Document , 表示文本文档。
• EditorView — NSTextView , 用 Combine 包装，绑定(bind)到 Document.content<String> .

Document是复杂 store:ObservableObject 的一部分, 所以它可以被限制为 EditorView实例。

当我第一次创建绑定(bind)时，它按预期工作——编辑 NSTextView 更改 Document.content 中的值.

let document1 = Document(...)
let document2 = Document(...)
var editor = EditorView(doc: document1)

但是如果改变绑定(bind)到另一个文档...

editor.doc = document2

...然后updateNSView可以看到新document2 .但是在 Coordiantor 的 textDidChange 里面仍然引用 document1 .

func textDidChange(_ notification: Notification) {
    guard let textView = notification.object as? NSTextView else {
        return
    }

    self.parent.doc.content = textView.string
    self.selectedRanges = textView.selectedRanges
}

所以，最初，当我设置新的 bindint 时，NSTextView 将其内容更改为 document2 , 但在我键入时，协调器将更改发送到 document1 .

是真的吗，Coordiantor 保留了它自己的 parent 副本，即使父级更改(@Binding doc 已更新)，它仍然引用旧的吗？

如何让 Coordinator 反射(reflect)父绑定(bind)的变化？

谢谢!

struct Document: Identifiable, Equatable {
    let id: UUID = UUID()
    var name: String
    var content: String
}

struct EditorView: NSViewRepresentable {
    @Binding var doc: Document

    func makeCoordinator() -> Coordinator {
        Coordinator(self)
    }

    func makeNSView(context: Context) -> CustomTextView {
        let textView = CustomTextView(
            text: doc.content,
            isEditable: isEditable,
            font: font
        )
        textView.delegate = context.coordinator

        return textView
    }

    func updateNSView(_ view: CustomTextView, context: Context) {
        view.text = doc.content
        view.selectedRanges = context.coordinator.selectedRanges

    }
}


// MARK: - Coordinator

extension EditorView {

    class Coordinator: NSObject, NSTextViewDelegate {
        var parent: EditorView
        var selectedRanges: [NSValue] = []

        init(_ parent: EditorView) {
            self.parent = parent
        }

        func textDidBeginEditing(_ notification: Notification) {
            guard let textView = notification.object as? NSTextView else {
                return
            }

            self.parent.doc.content = textView.string
            self.parent.onEditingChanged()
        }

        func textDidChange(_ notification: Notification) {
            guard let textView = notification.object as? NSTextView else {
                return
            }

            self.parent.doc.content = textView.string
            self.selectedRanges = textView.selectedRanges
        }

        func textDidEndEditing(_ notification: Notification) {
            guard let textView = notification.object as? NSTextView else {
                return
            }

            self.parent.doc.content = textView.string
            self.parent.onCommit()
        }
    }
}

// MARK: - CustomTextView

final class CustomTextView: NSView {
    private var isEditable: Bool
    private var font: NSFont?

    weak var delegate: NSTextViewDelegate?

    var text: String {
        didSet {
            textView.string = text
        }
    }
    // ...

Answer 1

Is it true, that Coordiantor keeps it's own copy of parent, and even if parent changes (@Binding doc is updated), it still references to old one?

一个parent，即这里的EditorView，是struct，所以答案是肯定的，一般是可以复制的。

How to make Coordinator reflect parent's bindings changes?

代替(或附加于)父级，将绑定(bind)显式注入(inject) Coordinator(通过构造函数)并直接使用它。