NavigationPath Experiments

ContentView.swift

//
//  ContentView.swift
//  NavigationTest
//
//  Created by Craig Hockenberry on 4/16/24.
//

import SwiftUI

struct OddView: View {
	@Binding var path: NavigationPath
	//@Binding var path: [PathOptions]
	
	var body: some View {
		Form {
			Section {
				NavigationLink("Foo", value: "Foo Value")
				NavigationLink("PIN", value: 1337)
				NavigationLink("Pathless", value: PathOptions.pathless)
				NavigationLink("First", value: PathOptions.first)
				NavigationLink("Second", value: PathOptions.second)
				NavigationLink("Third", value: PathOptions.third)
				NavigationLink("Fourth", value: PathOptions.fourth)
				NavigationLink("Fifth", value: PathOptions.fifth)
				Button("Remove Last") {
					path.removeLast()
				}
				Button("Back to Root") {
					path.removeLast(path.count)
				}
			}
			// NOTE: Disables selection completely. Not good.
			//.listRowBackground(Color(UIColor.systemBackground))
		}
		.formStyle(.grouped)
		.onAppear {
			print("OddView: path.count = \(path.count)")
		}
	}
}

struct EvenView: View {
	@Binding var path: NavigationPath
	//@Binding var path: [PathOptions]

	var body: some View {
		Form {
			Section {
				NavigationLink("Bar", value: "Bar Value")
				NavigationLink("PUNK", value: 999)
				NavigationLink("Pathless", value: PathOptions.pathless)
				NavigationLink("First", value: PathOptions.first)
				NavigationLink("Second", value: PathOptions.second)
				NavigationLink("Third", value: PathOptions.third)
				NavigationLink("Fourth", value: PathOptions.fourth)
				NavigationLink("Fifth", value: PathOptions.fifth)
				Button("Remove Last") {
					path.removeLast()
				}
				Button("Append First") {
					path.append(PathOptions.first)
				}
			}
		}
		.formStyle(.grouped)
		.onAppear {
			print("EvenView: path.count = \(path.count)")
		}
	}
}

struct PathlessView: View {
	var body: some View {
		Form {
			Section {
				NavigationLink("First", value: PathOptions.first)
				NavigationLink("Second", value: PathOptions.second)
				NavigationLink("Pathless", value: PathOptions.pathless)
			}
		}
		.formStyle(.grouped)
		.onAppear {
			print("PathlessView: no path binding")
		}
	}
}

enum PathOptions: String {
	case first
	case second
	case third
	case fourth
	case fifth
	case pathless
}

struct ContentView: View {
	@State private var path = NavigationPath()
	//@State private var path = [PathOptions.first, PathOptions.second]

	var body: some View {
		NavigationStack(path: $path) {
			Form {
				Section {
					NavigationLink("First", value: PathOptions.first)
					NavigationLink("Second", value: PathOptions.second)
				}
			}
			.formStyle(.grouped)
			.navigationTitle("ContentView")
			.navigationDestination(for: PathOptions.self) { pathOption in
				switch pathOption {
				case .first:
					OddView(path: $path)
						.navigationTitle("First")
				case .second:
					EvenView(path: $path)
						.navigationTitle("Second")
				case .third:
					OddView(path: $path)
						.navigationTitle("Third")
				case .fourth:
					EvenView(path: $path)
						.navigationTitle("Fourth")
				case .fifth:
					OddView(path: $path)
						.navigationTitle("Fifth")
				case .pathless:
					PathlessView()
						.navigationTitle("Pathless")
				}
			}
			.navigationDestination(for: String.self) { string in
				Text("View with '\(string)'")
					.navigationTitle(string)
			}
			.navigationDestination(for: Int.self) { int in
				Text("View with \(int)")
					.navigationTitle("\(int)")
			}
			.onAppear {
				print("ContentView: path = \(path.count)")
			}
		}
	}
}


#Preview {
	ContentView()
}

The issue is that the row values for the NavigationLink are used to determine identity (they must be Hashable). When you have a cyclical graph, you need something else to make the row unique. One option is to add a "level" to the items you add to the NavigationPath:

https://gist.github.com/phillipcaudell/fda686d67bde2f87a9252fbd802fcc3a

This causes the hash value for the row to be unique, even if the underlying data is not.