SwiftUIViewDebug

Background

In addition to View._printChanges and ViewModifier._printChanges for performance diagnosis, we can also use the method provided by SwiftUI._ViewDebug to get more debug info of SwiftUI View.

SwiftUI does not full exposed the debug info property for us to use directly. But we can encode it to Swift.Data, convert it to Swift.String and finally consume it by human readable JSON format.

Xcode's Debug View Hierarchy Window is probrobly using this method to get more debugging information.

Other UI debugging Application (such as Lookin) may also use such information to display more information of the SwiftUI view

Installation

let package = Package(
    dependencies: [
        .package(url: "https://github.com/Kyle-Ye/SwiftUIViewDebug", from: "1.0.0"),
    ],
    targets: [
        .target(name: <#Target Name#>, dependencies: [
            .product(name: "SwiftUIViewDebug", package: "SwiftUIViewDebug"),
        ]),
    ]
)

Example Usage

struct ContentView: View {
    var body: some View {
        VStack {
            Image(systemName: "globe")
                .imageScale(.large)
            Text("Hello, world!")
        }
        ._viewDebug(exportTo: FileManager.default.temporaryDirectory.appendingPathComponent("example.json"))
    }
}

See full example usage on Example/ExampleApp

The example output can be found at example.json

Explaination

Currently only _UIHostingView / NSHostingView exposes the _viewDebugData() method. So we need to wrap it in UIHostingController / NSHostingController to get the debug data.

If you are interested in the implementation detail of _ViewDebug, you can check my WIP implementation of _ViewDebug here.

License