feat: API & Performance Improvements

- Optimizations:
  - Destinations now use strong references to controllers and explicitly removes those references when controllers are popped from the navigation stack, no more just-in-case cleanups in StackDestination on each wrappedValue access
- API Improvements
  - With new navigationStack/Destination methods controllers can be implicitly instantiated from Destination wrappers, all users have to do is provide mappings from Route to a corresponding destination

Author: maximkrouk

Example/Sources/CombineNavigationExample/FeedTabFeature/FeedTabController.swift

@@ -58,12 +58,12 @@ public final class FeedTabController: ComposableViewControllerOf<FeedTabFeature>
 			publisher.map(\.path).removeDuplicates(by: { $0.ids == $1.ids }),
 			ids: \.ids,
 			route: { $0[id: $1] },
-			switch: destinations { destination, route, id in
+			switch: destinations { destinations, route in
 				switch route {
 				case .feed:
-					destination.$feedControllers[id]
+					destinations.$feedControllers
 				case .profile:
-					destination.$profileControllers[id]
+					destinations.$profileControllers
 				}
 			},
 			onPop: capture { _self, ids in

Example/Sources/CombineNavigationExample/TweetsFeedFeature/TweetsFeedController.swift

@@ -45,7 +45,7 @@ public final class TweetsFeedController: ComposableViewControllerOf<TweetsFeedFe
 		navigationDestination(
 			"reply_detail",
 			isPresented: publisher.detail.isNotNil,
-			controller: _detailController.callAsFunction,
+			destination: $detailController,
 			onPop: captureSend(.detail(.dismiss))
 		)
 		.store(in: &cancellables)

README.md

@@ -52,7 +52,7 @@ final class MyViewController: UIViewController {
       switch: destinations { destinations, route in
         switch route {
         case .details:
-          destinations.$detailsController()
+          destinations.$detailsController
         }
       },
       onPop: capture { _self in 
@@ -79,7 +79,7 @@ final class MyViewController: UIViewController {
     navigationDestination(
       "my_feature_details"
       isPresented: viewModel.publisher(for: \.state.detais.isNotNil),
-      controller: destinations { $0.$detailsController() },
+      destination: $detailsController,
       onPop: capture { $0.viewModel.send(.dismiss) }
     ).store(in: &cancellables)
   }
@@ -110,12 +110,12 @@ final class MyViewController: UIViewController {
   func bindViewModel() {
     navigationStack(
       viewModel.publisher(for: \.state.path),
-      switch: destinations { destinations, route, index in
+      switch: destinations { destinations, route in
         switch route {
         case .featureA:
-          destinations.$featureAControllers[index]
+          destinations.$featureAControllers
         case .featureB:
-          destinations.$featureBControllers[index]
+          destinations.$featureBControllers
         }
       },
       onPop: capture { _self, indices in

Sources/CombineNavigation/CocoaViewController+API.swift

@@ -9,6 +9,29 @@ import FoundationExtensions
 // MARK: navigationStack
 
 extension CocoaViewController {
+	/// Subscribes on publisher of navigation stack state
+	public func navigationStack<
+		P: Publisher,
+		C: Collection & Equatable,
+		Route: Hashable
+	>(
+		_ publisher: P,
+		switch destination: @escaping (Route) -> any GrouppedDestinationProtocol<C.Index>,
+		onPop: @escaping ([C.Index]) -> Void
+	) -> Cancellable where
+		P.Output == C,
+		P.Failure == Never,
+		C.Element == Route,
+		C.Index: Hashable,
+		C.Indices: Equatable
+	{
+		combineNavigationRouter.navigationStack(
+			publisher,
+			switch: destination,
+			onPop: onPop
+		)
+	}
+
 	/// Subscribes on publisher of navigation stack state
 	public func navigationStack<
 		P: Publisher,
@@ -32,6 +55,32 @@ extension CocoaViewController {
 		)
 	}
 
+	/// Subscribes on publisher of navigation stack state
+	public func navigationStack<
+		P: Publisher,
+		Stack,
+		IDs: Collection & Equatable,
+		Route
+	>(
+		_ publisher: P,
+		ids: @escaping (Stack) -> IDs,
+		route: @escaping (Stack, IDs.Element) -> Route?,
+		switch destination: @escaping (Route) -> any GrouppedDestinationProtocol<IDs.Element>,
+		onPop: @escaping ([IDs.Element]) -> Void
+	) -> Cancellable where
+		P.Output == Stack,
+		P.Failure == Never,
+		IDs.Element: Hashable
+	{
+		combineNavigationRouter.navigationStack(
+			publisher,
+			ids: ids,
+			route: route,
+			switch: destination,
+			onPop: onPop
+		)
+	}
+
 	/// Subscribes on publisher of navigation stack state
 	public func navigationStack<
 		P: Publisher,
@@ -62,6 +111,24 @@ extension CocoaViewController {
 // MARK: navigationDestination
 
 extension CocoaViewController {
+	/// Subscribes on publisher of navigation destination state
+	public func navigationDestination<P: Publisher>(
+		_ id: AnyHashable,
+		isPresented publisher: P,
+		destination: SingleDestinationProtocol,
+		onPop: @escaping () -> Void
+	) -> AnyCancellable where
+		P.Output == Bool,
+		P.Failure == Never
+	{
+		combineNavigationRouter.navigationDestination(
+			id,
+			isPresented: publisher,
+			destination: destination,
+			onPop: onPop
+		)
+	}
+
 	/// Subscribes on publisher of navigation destination state
 	public func navigationDestination<P: Publisher>(
 		_ id: AnyHashable,
@@ -80,6 +147,23 @@ extension CocoaViewController {
 		)
 	}
 
+	/// Subscribes on publisher of navigation destination state
+	public func navigationDestination<P: Publisher, Route>(
+		_ publisher: P,
+		switch destination: @escaping (Route) -> SingleDestinationProtocol,
+		onPop: @escaping () -> Void
+	) -> AnyCancellable where
+		Route: Hashable,
+		P.Output == Route?,
+		P.Failure == Never
+	{
+		combineNavigationRouter.navigationDestination(
+			publisher,
+			switch: destination,
+			onPop: onPop
+		)
+	}
+
 	/// Subscribes on publisher of navigation destination state
 	public func navigationDestination<P: Publisher, Route>(
 		_ publisher: P,

Sources/CombineNavigation/Destinations/StackDestination.swift

@@ -4,40 +4,54 @@ import CocoaAliases
 import Combine
 import FoundationExtensions
 
+public protocol GrouppedDestinationProtocol<DestinationID> {
+	associatedtype DestinationID: Hashable
+
+	@_spi(Internals)
+	func _initControllerIfNeeded(for id: DestinationID) -> CocoaViewController
+
+	@_spi(Internals)
+	func _invalidateDestination(for id: DestinationID)
+}
+
 /// Wrapper for creating and accessing managed navigation stack controllers
 @propertyWrapper
 open class StackDestination<
-	StackElementID: Hashable,
+	DestinationID: Hashable,
 	Controller: CocoaViewController
->: Weakifiable {
-	private var _controllers: [StackElementID: Weak<Controller>] = [:]
+>: Weakifiable, GrouppedDestinationProtocol {
+	@_spi(Internals)
+	open var _controllers: [DestinationID: Controller] = [:]
 
-	open var wrappedValue: [StackElementID: Controller] {
-		let controllers = _controllers.compactMapValues(\.wrappedValue)
-		_controllers = controllers.mapValues(Weak.init(wrappedValue:))
-		return controllers
+	open var wrappedValue: [DestinationID: Controller] {
+		_controllers
 	}
 
-	open var projectedValue: StackDestination<StackElementID, Controller> { self }
+	@inlinable
+	open var projectedValue: StackDestination<DestinationID, Controller> { self }
 
-	private var _initControllerOverride: ((StackElementID) -> Controller)?
+	@usableFromInline
+	internal var _initControllerOverride: ((DestinationID) -> Controller)?
 
-	private var _configuration: ((Controller, StackElementID) -> Void)?
+	@usableFromInline
+	internal var _configuration: ((Controller, DestinationID) -> Void)?
 
 	/// Sets instance-specific override for creating a new controller
 	///
 	/// This override has the highest priority when creating a new controller
 	///
 	/// To disable isntance-specific override pass `nil` to this method
+	@inlinable
 	public func overrideInitController(
-		with closure: ((StackElementID) -> Controller)?
+		with closure: ((DestinationID) -> Controller)?
 	) {
 		_initControllerOverride = closure
 	}
 
 	/// Sets instance-specific configuration for controllers
+	@inlinable
 	public func setConfiguration(
-		_ closure: ((Controller, StackElementID) -> Void)?
+		_ closure: ((Controller, DestinationID) -> Void)?
 	) {
 		_configuration = closure
 		closure.map { configure in
@@ -47,15 +61,19 @@ open class StackDestination<
 		}
 	}
 
-	@_spi(Internals) open class func initController(
-		for id: StackElementID
+	@_spi(Internals)
+	@inlinable
+	open class func initController(
+		for id: DestinationID
 	) -> Controller {
 		return Controller()
 	}
 
-	@_spi(Internals) open func configureController(
+	@_spi(Internals)
+	@inlinable
+	open func configureController(
 		_ controller: Controller,
-		for id: StackElementID
+		for id: DestinationID
 	) {}
 
 	/// Creates a new instance
@@ -70,16 +88,31 @@ open class StackDestination<
 	/// doesn't have a custom init you'll have to use this method or if you have a base controller that
 	/// requires custom init it'll be beneficial for you to create a custom subclass of StackDestination
 	/// and override it's `initController` class method, you can find an example in tests.
-	public convenience init(_ initControllerOverride: @escaping (StackElementID) -> Controller) {
+	@inlinable
+	public convenience init(_ initControllerOverride: @escaping (DestinationID) -> Controller) {
 		self.init()
 		self.overrideInitController(with: initControllerOverride)
 	}
 
+	@_spi(Internals)
+	@inlinable
+	public func _initControllerIfNeeded(
+		for id: DestinationID
+	) -> CocoaViewController {
+		return self[id]
+	}
+
+	@_spi(Internals)
+	@inlinable
+	open func _invalidateDestination(for id: DestinationID) {
+		self._controllers.removeValue(forKey: id)
+	}
+
 	/// Returns `wrappedValue[id]` if present, intializes and configures a new instance otherwise
-	public subscript(_ id: StackElementID) -> Controller {
+	public subscript(_ id: DestinationID) -> Controller {
 		let controller = wrappedValue[id] ?? {
 			let controller = _initControllerOverride?(id) ?? Self.initController(for: id)
-			_controllers[id] = Weak(controller)
+			_controllers[id] = controller
 			configureController(controller, for: id)
 			_configuration?(controller, id)
 			return controller
@@ -89,3 +122,10 @@ open class StackDestination<
 	}
 }
 #endif
+
+/*
+- Add erased protocols for Tree/StackDestination with some cleanup function
+- Make RoutingController.destinations method return an instance of the protocol
+- In CocoaViewController+API.swift add custom navigationStack/Destination methods
+- Those methods will inject cleanup function call into onPop handler
+*/