How to make a resizable HSplitView for macOS?

Any luck? I'm running into the same issues.

Nope. Spent a whole day trying to use VSplitView and HSplitView. They must be bugged atm.

With the new beta 2, the divider is resizable for me by default.

I am trying to simulate an NSOutlineView by using a sidebar with nested sublists:

struct ContentView : View {
    var body: some View {
        HSplitView() {
            List() {
                
                Section(header: Text("Section 1")) {
                    Text("Sub 1.1")
                    Text("Sub 1.2")
                }
                
                Section(header: Text("Section 2")) {
                    Text("Sub 2.1")
                    List {
                        Section(header: Text("Subsection 2.2")) {
                            Text("Sub 2.2.1")
                            Text("Sub 2.2.2")
                        }
                        Section(header: Text("Subsection 2.3")) {
                            Text("Sub 2.3.1")
                            Text("Sub 2.3.2")
                        }
                    } //.frame(height: 140)
                }
                
                Section(header: Text("Section 3")) {
                    Text("Sub 3.1")
                    Text("Sub 3.2")
                }
                
                }.listStyle(.sidebar)
            
            List() {
                Text("Content")
                Text("Content")
                Text("Content")
                Text("Content")
            }
        }
    }
}

By uncommenting the 22nd line, you can see and un/fold the sections of the second sublist, otherwise SwiftUI assigns a fixed height to all the sections. I can't find a simple way to force the height of a section to the intrinsic height of its content.

Assuming that you want to use the Master-Details pattern, I think that Approach should be to use Navigation Controls and not use the List (as list will require using binding and glue-code to display Details: this is a lot of work for a basic UI pattern, way too complex).

The Master-details pattern, on WWDC slides uses Navigation controls:

https://developer.apple.com/videos/play/wwdc2019/216/ at 55:10 and slide 278 onwards.

The issue appers to be that Mac implemention of SwitUI is pretty buggy and thus Navigation is not available. I am pretty sure that Developers at Apple are getting beaten eveyday to fix SwiftUI (fill the the gap between over-promised and under-delivered features).

I am skeptical that it Mac SwitUI will be even ready for September Release.

Does this implementation work as of beta 2? I just get a huge list, no master-detail.

Without navigation, the closest one can do is generate new views for every click

import SwiftUI

struct ContentView : View {
  
    @State var clickedContent: RandomListStruct?
    @State var clickedUseCase: Int?

    var var_list : [RandomListStruct]
    let zero = "use a default view as in WWDC video"

    var body: some View {
        HStack (alignment: .top) {

          
            VStack (alignment: .leading){

                List (selection: $clickedContent) {
                    Text ("Master Record").color(.orange)
                    Divider()

                    ForEach(var_list.identified(by: \.self)) { rls in
                        HStack {
                            Text("\(rls.name)")
                            Spacer()
                            Text("\(rls.address)")
                          
                        }
                    }
                }
            }.frame(maxWidth: 250, maxHeight: .infinity)
          
          
            VStack {
                List {
                    Text ("Details ").color(.orange)
                    Divider()
                    if (clickedContent?.name ?? zero) == zero {
                        Text("Please select a Row").color(.red)
                      
                    } else {
                        VStack(alignment: .leading) {
                          
                            Text("Name : \(clickedContent!.name)").color(.green)
                            Text("Address : \(clickedContent!.address)").color(.green)
                          
                        }
                      
                    }
                }
            }.frame(maxWidth: 500, maxHeight: .infinity)
          
        }
    }
}

struct RandomListStruct: Hashable, Codable, Identifiable {
    var id : Int
    var name : String
    var address : String
}

let var_list1 = [
    RandomListStruct(id: 1, name: "John", address: "200 Hollywood"),
    RandomListStruct(id: 2, name: "Jane", address: "212 Willowdale"),
    RandomListStruct(id: 3, name: "Ishan", address: "801 Elmwood"),
    RandomListStruct(id: 4, name: "Kris", address: "214 Front"),
    RandomListStruct(id: 5, name: "Ishani", address: "215 Bay St")
]

#if DEBUG
struct ContentView_Previews : PreviewProvider {
    static var previews: some View {
      
        ContentView(var_list: var_list1)
    }
}
#endif

I think I figured it out. Wrapping your main ContentView in GeometryReader and setting frame modifier to explicit gemoetry of the view worked for me:

struct ContentView: View {
     var body: some View {
        GeometryReader { geometry in
            VStack {
                HSplitView {
                    VStack { Text("Pane 1") }.frame(maxWidth: .infinity, maxHeight: .infinity)
                    VStack { Text("Pane 2") }.frame(maxWidth: .infinity, maxHeight: .infinity)
                }
            }.frame(width: geometry.size.width, height: geometry.size.height)
        }
     }
}