EasyFocus Example: Making it easier to set/get focus in your Lists.

EasyFocusExample.swift

//
//  Easy Focus Example
//
// The package allows the code below to focus (🙂) on the data
// that is changing, and not on underlying id records as is required
// when using @FocusState.
// Code differences when using this package are highlighted
// below with /*👉*/
//
//  Created by Andrew Cowley on 21/11/2021.
//

import SwiftUI
import EasyFocus // https://github.com/disc0infern0/EasyFocus

struct ContentView: View {
   @StateObject
   var vm = GenericFocusViewModel()
   var body: some View {
      GenericFocusExample()
         .environmentObject(vm)
   }
}

struct ContentView_Previews: PreviewProvider {
   static var previews: some View {
      ContentView()
   }
}

struct GenericFocusExample: View {
   @EnvironmentObject
   var vm: GenericFocusViewModel
/*👉*/@Focus   // not @FocusState
   private var focusedRow: FocusDataModelExample?
   var body: some View {
      VStack {
         List {
            ForEach($vm.data) { $row in
               TextField("row text", text: $row.text)
/*👉*/ 	  	   	.enableFocus(on: row, with: _focusedRow)
                  .onSubmit { vm.newRow() }
            }
         }
         .animation(.easeInOut, value: vm.data)
/*👉*/   .sync( $vm.focusedRow, _focusedRow )

         Button("Print current row text, then goto row \(vm.randomRow+1)") {
            vm.buttonPress()
         }
         .buttonStyle(.borderedProminent)
      }
   }
}

class GenericFocusViewModel: ObservableObject {
   @Published
   var data = FocusDataModelExample.examples
   @Published
   var focusedRow: FocusDataModelExample?
   @Published
   var randomRow: Int = 0  // For settng focus to random rows

   /// Add a new row to the collection immediate after the currently focused row,
   /// and then set the focus to the new row
   func newRow() {
      let newRow = FocusDataModelExample()
      if let id = focusedRow?.id,
         let ind = data.firstIndex(where: {$0.id == id}) {
         data.insert(newRow, at: data.index(after: ind))
      } else {
         data.append(newRow)
      }
/*👉*/focusedRow = newRow
   }
   /// Prints the text on the currently focused row, moves the focus
   /// to a new row indicated on the button, then sets a new random(*) row
   /// for the next button press. (*): excludes currrent row.
   func buttonPress() {
      print(focusedRow?.text ?? "") // uses the get
/*👉*/focusedRow = data[randomRow]
/*👉*/randomRow = (0..<data.count)
         .filter({ $0 != randomRow})
         .randomElement()!
   }
   init() {
      randomRow = Int.random(in: 0..<data.count)
   }

   func indexAfter(_ id: String) -> Int {
      let currentIndex = data.firstIndex(where: {$0.id == id}) ?? data.endIndex
      return data.index(after: currentIndex )
   }
}

struct FocusDataModelExample: FocusableListRow {
   // N.B. We could have picked any datatype for our id, as long as it satisfies Identifiable & Equatable
   var id = UUID().uuidString
   var text: String = ""

   static var examples = [ FocusDataModelExample(id: "1", text: "one"),
                           FocusDataModelExample(id: "2", text: "two"),
                           FocusDataModelExample(id: "3", text: "three") ]
}