Fix ObjC export of MultilinePillPickerView (#2122)

Sources/FluentUI_macOS/Components/MultilinePillPicker/MultilinePillPickerView.swift

@@ -4,12 +4,13 @@
 //
 
 import AppKit
+import Combine
 import SwiftUI
 
 /// This is a work-in-progress control for hosting multiple rows of pill buttons. At present, this control
 /// only supports a hard-coded two rows of elements.
 @objc(MSFMultilinePillPickerView)
-public final class MultilinePillPickerView: ControlHostingView {
+public final class MultilinePillPickerView: ControlHostingView, ObservableObject {
 	/// Creates a multiline pill picker.
 	/// - Parameters:
 	///   - labels: An array of labels to show in the picker.
@@ -18,37 +19,48 @@ public final class MultilinePillPickerView: ControlHostingView {
 	@MainActor public init(labels: [String], action: (@MainActor (Int) -> Void)? = nil) {
 		self.labels = labels
 		self.action = action
-		let picker = MultilinePillPicker(labels: labels, action: action)
-		super.init(AnyView(picker))
+		super.init(AnyView(EmptyView()))
+
+		let wrapper = MultilinePillPickerWrapper(viewModel: viewModel)
+		self.hostingView.rootView = AnyView(wrapper)
+
+		// Set up observation to keep the view model in sync.
+		bindProperty(from: self.$isEnabled, to: \.isEnabled, on: viewModel)
+		bindProperty(from: self.$labels, to: \.labels, on: viewModel)
+		bindProperty(from: self.$action, to: \.action, on: viewModel)
 	}
 
 	@MainActor required dynamic init?(coder aDecoder: NSCoder) {
-		fatalError("init(coder:) has not been implemented")
+		preconditionFailure("init(coder:) has not been implemented")
 	}
 
 	@MainActor required init(rootView: AnyView) {
-		fatalError("init(rootView:) has not been implemented")
+		preconditionFailure("init(rootView:) has not been implemented")
 	}
 
-	@MainActor public var isEnabled: Bool = true {
-		didSet {
-			updatePicker()
-		}
-	}
-	@MainActor public var labels: [String] {
-		didSet {
-			updatePicker()
-		}
-	}
-	@MainActor public var action: (@MainActor (Int) -> Void)? {
-		didSet {
-			updatePicker()
-		}
-	}
+	@MainActor @Published public var isEnabled: Bool = true
+	@MainActor @Published public var labels: [String]
+	@MainActor @Published public var action: (@MainActor (Int) -> Void)?
+
+	@MainActor private let viewModel: MultilinePillPickerViewModel = .init()
+}
+
+/// Maps properties from `MultilinePillPickerView` to `MultilinePillPickerViewWrapper`.
+fileprivate class MultilinePillPickerViewModel: ObservableObject {
+	@Published var isEnabled: Bool = true
+	@Published var labels: [String] = []
+	@Published var action: (@MainActor (Int) -> Void)?
+}
+
+/// Private wrapper `View` to map from view model to `MultilinePillPicker`.
+fileprivate struct MultilinePillPickerWrapper: View {
+	@ObservedObject var viewModel: MultilinePillPickerViewModel
 
-	private func updatePicker() {
-		let picker = MultilinePillPicker(labels: labels, action: action)
-			.disabled(!isEnabled)
-		rootView = AnyView(picker)
+	var body: some View {
+		MultilinePillPicker(
+			labels: viewModel.labels,
+			action: viewModel.action
+		)
+		.disabled(!viewModel.isEnabled)
 	}
 }

Sources/FluentUI_macOS/Core/ControlHostingView.swift

@@ -4,10 +4,18 @@
 //
 
 import AppKit
+import Combine
 import SwiftUI
 
-/// Common wrapper for hosting and exposing SwiftUI components to AppKit-based clients.
-open class ControlHostingView: NSHostingView<AnyView> {
+/// Common wrapper for hosting and exposing SwiftUI components to UIKit-based clients.
+open class ControlHostingView: NSView {
+
+	/// The intrinsic content size of the wrapped SwiftUI view.
+	@objc public override var intrinsicContentSize: CGSize {
+		// Our desired size should always be the same as our hosted view.
+		return hostingView.intrinsicContentSize
+	}
+
 	/// Initializes and returns an instance of `ControlHostingContainer` that wraps `controlView`.
 	///
 	/// Unfortunately this class can't use Swift generics, which are incompatible with Objective-C interop. Instead we have to wrap
@@ -17,21 +25,50 @@ open class ControlHostingView: NSHostingView<AnyView> {
 	/// - Parameter safeAreaRegions: Passthrough to the respective property on NSHostingView.
 	/// Indicates which safe area regions the underlying hosting controller should add to its view.
 	public init(_ controlView: AnyView, safeAreaRegions: SafeAreaRegions = .all) {
-		super.init(rootView: controlView)
+		hostingView = NSHostingView.init(rootView: controlView)
 		if #available(macOS 13.3, *) {
-			self.sizingOptions = [.intrinsicContentSize]
-			self.safeAreaRegions = safeAreaRegions
+			hostingView.sizingOptions = [.intrinsicContentSize]
+			hostingView.safeAreaRegions = safeAreaRegions
 		}
 
-		layer?.backgroundColor = .clear
-		translatesAutoresizingMaskIntoConstraints = false
+		super.init(frame: .zero)
+
+		self.configureHostedView()
 	}
 
-	@MainActor @preconcurrency required public init?(coder: NSCoder) {
+	required public init?(coder: NSCoder) {
 		preconditionFailure("init(coder:) has not been implemented")
 	}
-
-	@MainActor @preconcurrency required public init(rootView: AnyView) {
-		preconditionFailure("init(rootView:) has not been implemented")
+
+	let hostingView: NSHostingView<AnyView>
+	var cancellables: Set<AnyCancellable> = []
+
+	// Helper function to facilitate binding ourselves to a ViewModel.
+	func bindProperty<Root: AnyObject, Value>(
+		from source: Published<Value>.Publisher,
+		to viewModelKeyPath: ReferenceWritableKeyPath<Root, Value>,
+		on viewModel: Root
+	) {
+		source
+			.sink { [weak viewModel] newValue in
+				viewModel?[keyPath: viewModelKeyPath] = newValue
+			}
+			.store(in: &cancellables)
+	}
+
+	/// Adds `hostingController.view` to ourselves as a subview, and enables necessary constraints.
+	private func configureHostedView() {
+		hostingView.layer?.backgroundColor = NSColor.clear.cgColor
+
+		addSubview(hostingView)
+		hostingView.translatesAutoresizingMaskIntoConstraints = false
+
+		let requiredConstraints = [
+			hostingView.leadingAnchor.constraint(equalTo: leadingAnchor),
+			hostingView.trailingAnchor.constraint(equalTo: trailingAnchor),
+			hostingView.bottomAnchor.constraint(equalTo: bottomAnchor),
+			hostingView.topAnchor.constraint(equalTo: topAnchor)
+		]
+		self.addConstraints(requiredConstraints)
 	}
 }