SwiftUI _viewDebugData

_ViewDebug.Property.swift

// SwiftUI public _ViewDebug.Property definition

public enum _ViewDebug {
  public enum Property : Swift.UInt32, Swift.Hashable {
    case type
    case value
    case transform
    case position
    case size
    case environment
    case phase
    case layoutComputer
    case displayList
    public init?(rawValue: Swift.UInt32)
    public typealias RawValue = Swift.UInt32
    public var rawValue: Swift.UInt32 { get }
  }
}

ConsoleOutput.txt

// Output of print(_viewDebugData), formatted for easier viewing

[SwiftUI._ViewDebug.Data(
  data: [
    SwiftUI._ViewDebug.Property.value: SwiftUI._SafeAreaInsetsModifier(elements: [], nextInsets: nil),
    SwiftUI._ViewDebug.Property.displayList: (display-list
      (item #:identity 2 #:version 6
        (frame (143.66666666666666 354.0; 88.0 20.333333333333332))
        (text "Hello World" #:size (88.0, 20.333333333333332))
      )
    ),
    SwiftUI._ViewDebug.Property.size: (375.0, 728.0), 
    SwiftUI._ViewDebug.Property.position: (0.0, 0.0), 
    SwiftUI._ViewDebug.Property.transform: translate(0.0, -50.0), space(HostingViewCoordinateSpace()), 
    SwiftUI._ViewDebug.Property.type: SwiftUI._SafeAreaInsetsModifier
  ],
  childData: [
    SwiftUI._ViewDebug.Data(
      data: [
        SwiftUI._ViewDebug.Property.transform: translate(0.0, -50.0), space(HostingViewCoordinateSpace()); sizedSpace(UniqueID(value: 77), 375.0, 728.0), 
        SwiftUI._ViewDebug.Property.position: (143.5, 353.8333333333333),
        SwiftUI._ViewDebug.Property.type: SwiftUI.ModifiedContent<SwiftUI.ModifiedContent<Previews.HelloWorldView, SwiftUI.EditModeScopeModifier>, SwiftUI.HitTestBindingModifier>, 
        SwiftUI._ViewDebug.Property.value: SwiftUI.ModifiedContent<SwiftUI.ModifiedContent<Previews.HelloWorldView, SwiftUI.EditModeScopeModifier>, SwiftUI.HitTestBindingModifier>(
          content: SwiftUI.ModifiedContent<Previews.HelloWorldView, SwiftUI.EditModeScopeModifier>(
            content: Previews.HelloWorldView(),
            modifier: SwiftUI.EditModeScopeModifier(_editMode: SwiftUI.State<SwiftUI.EditMode>(_value: SwiftUI.EditMode.inactive, _location: nil))
          ),
          modifier: SwiftUI.HitTestBindingModifier()
        ),
        SwiftUI._ViewDebug.Property.size: (88.0, 20.333333333333332)
      ],
      childData: [
        SwiftUI._ViewDebug.Data(
          data: [
            SwiftUI._ViewDebug.Property.value: SwiftUI.HitTestBindingModifier(),
            SwiftUI._ViewDebug.Property.type: SwiftUI.HitTestBindingModifier
        ],
        childData: [
          SwiftUI._ViewDebug.Data(
            data: [
              SwiftUI._ViewDebug.Property.type: SwiftUI.ModifiedContent<Previews.HelloWorldView, SwiftUI.EditModeScopeModifier>, 
              SwiftUI._ViewDebug.Property.value: SwiftUI.ModifiedContent<Previews.HelloWorldView, SwiftUI.EditModeScopeModifier>(
                content: Previews.HelloWorldView(), 
                modifier: SwiftUI.EditModeScopeModifier(_editMode: SwiftUI.State<SwiftUI.EditMode>(_value: SwiftUI.EditMode.inactive, _location: nil))
              )
            ],
            childData: [
              SwiftUI._ViewDebug.Data(
                data: [
                  SwiftUI._ViewDebug.Property.type: SwiftUI.EditModeScopeModifier,
                  SwiftUI._ViewDebug.Property.value: SwiftUI.EditModeScopeModifier(_editMode: SwiftUI.State<SwiftUI.EditMode>(_value: SwiftUI.EditMode.inactive, _location: nil))
                ],
                childData: [
                  SwiftUI._ViewDebug.Data(
                    data: [
                      SwiftUI._ViewDebug.Property.value: SwiftUI.ModifiedContent<SwiftUI._ViewModifier_Content<SwiftUI.EditModeScopeModifier>,
                      SwiftUI._EnvironmentKeyWritingModifier<Swift.Optional<SwiftUI.Binding<SwiftUI.EditMode>>>>(content: SwiftUI._ViewModifier_Content<SwiftUI.EditModeScopeModifier>(), modifier: SwiftUI._EnvironmentKeyWritingModifier<Swift.Optional<SwiftUI.Binding<SwiftUI.EditMode>>>(keyPath: Swift.WritableKeyPath<SwiftUI.EnvironmentValues, Swift.Optional<SwiftUI.Binding<SwiftUI.EditMode>>>, value: Optional(SwiftUI.Binding<SwiftUI.EditMode>(transaction: SwiftUI.Transaction(plist: []), location: SwiftUI.StoredLocation<SwiftUI.EditMode>, _value: SwiftUI.EditMode.inactive)))),
                      SwiftUI._ViewDebug.Property.type: SwiftUI.ModifiedContent<SwiftUI._ViewModifier_Content<SwiftUI.EditModeScopeModifier>, SwiftUI._EnvironmentKeyWritingModifier<Swift.Optional<SwiftUI.Binding<SwiftUI.EditMode>>>>
                    ],
                    childData: [
                      SwiftUI._ViewDebug.Data(
                        data: [
                          SwiftUI._ViewDebug.Property.value: SwiftUI._EnvironmentKeyWritingModifier<Swift.Optional<SwiftUI.Binding<SwiftUI.EditMode>>>(keyPath: Swift.WritableKeyPath<SwiftUI.EnvironmentValues, Swift.Optional<SwiftUI.Binding<SwiftUI.EditMode>>>, value: Optional(SwiftUI.Binding<SwiftUI.EditMode>(transaction: SwiftUI.Transaction(plist: []), location: SwiftUI.StoredLocation<SwiftUI.EditMode>, _value: SwiftUI.EditMode.inactive))), 
                          SwiftUI._ViewDebug.Property.type: SwiftUI._EnvironmentKeyWritingModifier<Swift.Optional<SwiftUI.Binding<SwiftUI.EditMode>>>
                        ],
                        childData: [
                          SwiftUI._ViewDebug.Data(
                            data: [
                              SwiftUI._ViewDebug.Property.value: SwiftUI._ViewModifier_Content<SwiftUI.EditModeScopeModifier>(), 
                              SwiftUI._ViewDebug.Property.type: SwiftUI._ViewModifier_Content<SwiftUI.EditModeScopeModifier>
                            ],
                            childData: [
                              SwiftUI._ViewDebug.Data(
                                data: [
                                  SwiftUI._ViewDebug.Property.value: Previews.HelloWorldView(),
                                  SwiftUI._ViewDebug.Property.type: Previews.HelloWorldView
                                ],
                                childData: [
                                  SwiftUI._ViewDebug.Data(
                                    data: [
                                      SwiftUI._ViewDebug.Property.value: SwiftUI.Text(storage: SwiftUI.Text.Storage.anyTextStorage(SwiftUI.(unknown context at $10f32f608).LocalizedTextStorage), modifiers: []), 
                                      SwiftUI._ViewDebug.Property.type: SwiftUI.Text
                                    ],
                                    childData: [
                                      SwiftUI._ViewDebug.Data(
                                        data: [
                                          SwiftUI._ViewDebug.Property.value: SwiftUI.AccessibilityStyledTextContentView(text: Hello World, unresolvedText: SwiftUI.Text(storage: SwiftUI.Text.Storage.anyTextStorage(SwiftUI.(unknown context at $10f32f608).LocalizedTextStorage), modifiers: [])), 
                                          SwiftUI._ViewDebug.Property.type: SwiftUI.AccessibilityStyledTextContentView
                                        ],
                                        childData: [
                                          SwiftUI._ViewDebug.Data(
                                            data: [
                                              SwiftUI._ViewDebug.Property.type: SwiftUI.ModifiedContent<SwiftUI.StyledTextContentView, SwiftUI.AccessibilityAttachmentModifier>,
                                              SwiftUI._ViewDebug.Property.value: SwiftUI.ModifiedContent<SwiftUI.StyledTextContentView, SwiftUI.AccessibilityAttachmentModifier>(
                                                content: SwiftUI.StyledTextContentView(text: Hello World), 
                                                modifier: SwiftUI.AccessibilityAttachmentModifier(storage: SwiftUI.AccessibilityAttachmentModifier.(unknown context at $10f317b48).Storage.propertiesComponent([SwiftUI.(unknown context at $10f317958).ReplacingPropertiesComponent<SwiftUI.AccessibilityNullableOptionSet<SwiftUI.AccessibilityVisibility>>, SwiftUI.(unknown context at $10f317958).ReplacingPropertiesComponent<Swift.Optional<() -> SwiftUI.AXAnyViewTypeDescribingBox>>, SwiftUI.(unknown context at $10f317958).ReplacingPropertiesComponent<Swift.Optional<SwiftUI.Text>>, SwiftUI.(unknown context at $10f317a28).CombiningPropertiesComponent<SwiftUI.AccessibilityNullableOptionSet<SwiftUI.AccessibilityTraitSet>>])))
                                              ],
                                              childData: [
                                                SwiftUI._ViewDebug.Data(
                                                  data: [
                                                    SwiftUI._ViewDebug.Property.type: SwiftUI.AccessibilityAttachmentModifier, 
                                                    SwiftUI._ViewDebug.Property.value: SwiftUI.AccessibilityAttachmentModifier(storage: SwiftUI.AccessibilityAttachmentModifier.(unknown context at $10f317b48).Storage.propertiesComponent([SwiftUI.(unknown context at $10f317958).ReplacingPropertiesComponent<SwiftUI.AccessibilityNullableOptionSet<SwiftUI.AccessibilityVisibility>>, SwiftUI.(unknown context at $10f317958).ReplacingPropertiesComponent<Swift.Optional<() -> SwiftUI.AXAnyViewTypeDescribingBox>>, SwiftUI.(unknown context at $10f317958).ReplacingPropertiesComponent<Swift.Optional<SwiftUI.Text>>, SwiftUI.(unknown context at $10f317a28).CombiningPropertiesComponent<SwiftUI.AccessibilityNullableOptionSet<SwiftUI.AccessibilityTraitSet>>]))
                                                  ], 
                                                childData: [
                                                  SwiftUI._ViewDebug.Data(
                                                    data: [
                                                      SwiftUI._ViewDebug.Property.type: SwiftUI.StyledTextContentView,
                                                      SwiftUI._ViewDebug.Property.displayList: (display-list
                                                        (item #:identity 2 #:version 6
                                                          (frame (143.66666666666666 354.0; 88.0 20.333333333333332))
                                                          (text "Hello World" #:size (88.0, 20.333333333333332))
                                                        )
                                                      ),
                                                      SwiftUI._ViewDebug.Property.value: SwiftUI.StyledTextContentView(text: Hello World)
                                                    ], 
                                                    childData: []
)])])])])])])])])])])])])])]

From where _viewDebugData comes?

It's a private property on UIHostingController's view (_UIHostingView):
https://apurin.me/articles/swiftui-secrets/

Thanks. Apparently things have changed across SwiftUI versions. This is now called makeViewDebugData and produce Data, which contains a very large JSON.

(lldb) po type(of: view.value(forKey: "makeViewDebugData")!)
Foundation.__NSSwiftData 

I'm not sure how it can be mapped to _ViewDebug, but the unsafeBitCast from the article does not work as is and probably needs some tweaking.