V1 API

KMPObservableViewModelCore/ChildViewModels.swift

@@ -9,19 +9,11 @@ import KMPObservableViewModelCoreObjC
 
 public extension ViewModel {
 
-    private func setChildViewModelPublishers(_ keyPath: AnyKeyPath, _ publishers: AnyHashable?) {
-        if let publishers = publishers {
-            observableViewModelPublishers(for: self).childPublishers[keyPath] = publishers
-        } else {
-            observableViewModelPublishers(for: self).childPublishers.removeValue(forKey: keyPath)
-        }
-    }
-
     private func setChildViewModel<VM: ViewModel>(
         _ viewModel: VM?,
         at keyPath: AnyKeyPath
     ) {
-        setChildViewModelPublishers(keyPath, observableViewModelPublishers(for: viewModel))
+        viewModelWillChange.cancellable.setChildCancellables(keyPath, ViewModelCancellable.get(for: viewModel))
     }
 
     /// Stores a reference to the `ObservableObject` for the specified child `ViewModel`.
@@ -48,8 +40,8 @@ public extension ViewModel {
         _ viewModels: [VM?]?,
         at keyPath: AnyKeyPath
     ) {
-        setChildViewModelPublishers(keyPath, viewModels?.map { viewModel in
-            observableViewModelPublishers(for: viewModel)
+        viewModelWillChange.cancellable.setChildCancellables(keyPath, viewModels?.map { viewModel in
+            ViewModelCancellable.get(for: viewModel)
         })
     }
 
@@ -95,8 +87,8 @@ public extension ViewModel {
         _ viewModels: Set<VM?>?,
         at keyPath: AnyKeyPath
     ) {
-        setChildViewModelPublishers(keyPath, viewModels?.map { viewModel in
-            observableViewModelPublishers(for: viewModel)
+        viewModelWillChange.cancellable.setChildCancellables(keyPath, viewModels?.map { viewModel in
+            ViewModelCancellable.get(for: viewModel)
         })
     }
 
@@ -142,8 +134,8 @@ public extension ViewModel {
         _ viewModels: [Key : VM?]?,
         at keyPath: AnyKeyPath
     ) {
-        setChildViewModelPublishers(keyPath, viewModels?.mapValues { viewModel in
-            observableViewModelPublishers(for: viewModel)
+        viewModelWillChange.cancellable.setChildCancellables(keyPath, viewModels?.mapValues { viewModel in
+            ViewModelCancellable.get(for: viewModel)
         })
     }
 

KMPObservableViewModelCore/ObservableViewModel.swift

@@ -13,8 +13,7 @@ import KMPObservableViewModelCoreObjC
 public func observableViewModel<VM: ViewModel>(
     for viewModel: VM
 ) -> ObservableViewModel<VM> {
-    let publishers = observableViewModelPublishers(for: viewModel)
-    return ObservableViewModel(publishers, viewModel)
+    return ObservableViewModel(viewModel)
 }
 
 /// Gets an `ObservableObject` for the specified `ViewModel`.
@@ -35,13 +34,13 @@ public final class ObservableViewModel<VM: ViewModel>: ObservableObject, Hashabl
     /// The observed `ViewModel`.
     public let viewModel: VM
 
-    /// Holds a strong reference to the publishers
-    private let publishers: ObservableViewModelPublishers
+    /// Holds a strong reference to the cancellable
+    private let cancellable: AnyCancellable
 
-    internal init(_ publishers: ObservableViewModelPublishers, _ viewModel: VM) {
-        objectWillChange = publishers.publisher
+    internal init(_ viewModel: VM) {
+        objectWillChange = viewModel.viewModelWillChange
         self.viewModel = viewModel
-        self.publishers = publishers
+        cancellable = ViewModelCancellable.get(for: viewModel)
     }
 
     public static func == (lhs: ObservableViewModel<VM>, rhs: ObservableViewModel<VM>) -> Bool {

KMPObservableViewModelCore/ObservableViewModelPublisher.swift

@@ -9,36 +9,27 @@ import Combine
 import KMPObservableViewModelCoreObjC
 
 /// Publisher for `ObservableViewModel` that connects to the `ViewModelScope`.
-public final class ObservableViewModelPublisher: Publisher {
+public final class ObservableViewModelPublisher: Combine.Publisher, KMPObservableViewModelCoreObjC.Publisher {
     public typealias Output = Void
     public typealias Failure = Never
 
-    internal weak var viewModel: (any ViewModel)?
+    internal let cancellable = ViewModelCancellable()
 
-    private let publisher = ObservableObjectPublisher()
-    private var objectWillChangeCancellable: AnyCancellable? = nil
+    private let publisher: ObservableObjectPublisher
+    private let subscriptionCount: any SubscriptionCount
 
-    internal init(_ viewModel: any ViewModel, _ objectWillChange: ObservableObjectPublisher) {
-        self.viewModel = viewModel
-        viewModel.viewModelScope.setSendObjectWillChange { [weak self] in
-            self?.publisher.send()
-        }
-        objectWillChangeCancellable = objectWillChange.sink { [weak self] _ in
-            self?.publisher.send()
-        }
+    internal init(_ viewModel: any ViewModel) {
+        self.publisher = viewModel.objectWillChange
+        self.subscriptionCount = viewModel.viewModelScope.subscriptionCount
     }
 
     public func receive<S>(subscriber: S) where S : Subscriber, Never == S.Failure, Void == S.Input {
-        viewModel?.viewModelScope.increaseSubscriptionCount()
-        publisher.receive(subscriber: ObservableViewModelSubscriber(self, subscriber))
+        subscriptionCount.increase()
+        publisher.receive(subscriber: ObservableViewModelSubscriber(subscriptionCount, subscriber))
     }
 
-    deinit {
-        guard let viewModel else { return }
-        if let cancellable = viewModel as? Cancellable {
-            cancellable.cancel()
-        }
-        viewModel.clear()
+    public func send() {
+        publisher.send()
     }
 }
 
@@ -47,16 +38,16 @@ private class ObservableViewModelSubscriber<S>: Subscriber where S : Subscriber,
     typealias Input = Void
     typealias Failure = Never
 
-    private let publisher: ObservableViewModelPublisher
+    private let subscriptionCount: any SubscriptionCount
     private let subscriber: S
 
-    init(_ publisher: ObservableViewModelPublisher, _ subscriber: S) {
-        self.publisher = publisher
+    init(_ subscriptionCount: any SubscriptionCount, _ subscriber: S) {
+        self.subscriptionCount = subscriptionCount
         self.subscriber = subscriber
     }
 
     func receive(subscription: Subscription) {
-        subscriber.receive(subscription: ObservableViewModelSubscription(publisher, subscription))
+        subscriber.receive(subscription: ObservableViewModelSubscription(subscriptionCount, subscription))
     }
 
     func receive(_ input: Void) -> Subscribers.Demand {
@@ -71,24 +62,21 @@ private class ObservableViewModelSubscriber<S>: Subscriber where S : Subscriber,
 /// Subscription for `ObservableViewModelPublisher` that decreases the subscription count upon cancellation.
 private class ObservableViewModelSubscription: Subscription {
 
-    private let publisher: ObservableViewModelPublisher
+    private var subscriptionCount: (any SubscriptionCount)?
     private let subscription: Subscription
 
-    init(_ publisher: ObservableViewModelPublisher, _ subscription: Subscription) {
-        self.publisher = publisher
+    init(_ subscriptionCount: any SubscriptionCount, _ subscription: Subscription) {
+        self.subscriptionCount = subscriptionCount
         self.subscription = subscription
     }
 
     func request(_ demand: Subscribers.Demand) {
         subscription.request(demand)
     }
 
-    private var cancelled = false
-
     func cancel() {
         subscription.cancel()
-        guard !cancelled else { return }
-        cancelled = true
-        publisher.viewModel?.viewModelScope.decreaseSubscriptionCount()
+        subscriptionCount?.decrease()
+        subscriptionCount = nil
     }
 }

KMPObservableViewModelCore/ViewModel.swift

@@ -8,11 +8,24 @@
 import Combine
 import KMPObservableViewModelCoreObjC
 
-/// A Kotlin Multiplatform Mobile ViewModel.
+/// A Kotlin Multiplatform ViewModel.
 public protocol ViewModel: ObservableObject where ObjectWillChangePublisher == ObservableObjectPublisher {
     /// The `ViewModelScope` of this `ViewModel`.
     var viewModelScope: ViewModelScope { get }
+    /// An `ObservableViewModelPublisher` that emits before this `ViewModel` has changed.
+    var viewModelWillChange: ObservableViewModelPublisher { get }
     /// Internal KMP-ObservableViewModel function used to clear the ViewModel.
     /// - Warning: You should NOT call this yourself!
     func clear()
 }
+
+public extension ViewModel {
+    var viewModelWillChange: ObservableViewModelPublisher {
+        if let publisher = viewModelScope.publisher {
+            return publisher as! ObservableViewModelPublisher
+        }
+        let publisher = ObservableViewModelPublisher(self)
+        viewModelScope.publisher = publisher
+        return publisher
+    }
+}

KMPObservableViewModelCore/ViewModelCancellable.swift

@@ -0,0 +1,53 @@
+//
+//  ViewModelCancellable.swift
+//  KMPObservableViewModelCore
+//
+//  Created by Rick Clephas on 09/06/2025.
+//
+
+import Combine
+
+/// Helper object that provides a weakly cached `Cancellable` for a `ViewModel`.
+internal class ViewModelCancellable {
+
+    private var didInit = false
+    private weak var cancellable: AnyCancellable?
+    private var childCancellables: Dictionary<AnyKeyPath, AnyHashable>? = [:]
+
+    private func get(_ viewModel: any ViewModel) -> AnyCancellable {
+        guard didInit else {
+            let cancellable = AnyCancellable {
+                if let cancellable = viewModel as? Cancellable {
+                    cancellable.cancel()
+                }
+                self.childCancellables = nil
+                viewModel.clear()
+            }
+            self.cancellable = cancellable
+            didInit = true
+            return cancellable
+        }
+        guard let cancellable = self.cancellable else {
+            fatalError("ObservableViewModel for \(viewModel) has been deallocated")
+        }
+        return cancellable
+    }
+
+    func setChildCancellables(_ keyPath: AnyKeyPath, _ cancellables: AnyHashable?) {
+        if let cancellables = cancellables {
+            childCancellables?[keyPath] = cancellables
+        } else {
+            childCancellables?.removeValue(forKey: keyPath)
+        }
+    }
+
+    static func get(for viewModel: any ViewModel) -> AnyCancellable {
+        viewModel.viewModelWillChange.cancellable.get(viewModel)
+    }
+
+    static func get(for viewModel: (any ViewModel)?) -> AnyCancellable? {
+        guard let viewModel else { return nil }
+        let cancellable = get(for: viewModel)
+        return cancellable
+    }
+}

KMPObservableViewModelCoreObjC/KMPOVMPublisher.h

@@ -0,0 +1,22 @@
+//
+//  KMPOVMPublisher.h
+//  KMPObservableViewModelCoreObjC
+//
+//  Created by Rick Clephas on 09/06/2025.
+//
+
+#ifndef KMPOVMPublisher_h
+#define KMPOVMPublisher_h
+
+#import <Foundation/Foundation.h>
+
+NS_ASSUME_NONNULL_BEGIN
+
+__attribute__((swift_name("Publisher")))
+@protocol KMPOVMPublisher
+- (void)send;
+@end
+
+NS_ASSUME_NONNULL_END
+
+#endif /* KMPOVMPublisher_h */

KMPObservableViewModelCoreObjC/KMPOVMSubscriptionCount.h

@@ -0,0 +1,23 @@
+//
+//  KMPOVMSubscriptionCount.h
+//  KMPObservableViewModelCoreObjC
+//
+//  Created by Rick Clephas on 09/06/2025.
+//
+
+#ifndef KMPOVMSubscriptionCount_h
+#define KMPOVMSubscriptionCount_h
+
+#import <Foundation/Foundation.h>
+
+NS_ASSUME_NONNULL_BEGIN
+
+__attribute__((swift_name("SubscriptionCount")))
+@protocol KMPOVMSubscriptionCount
+- (void)increase;
+- (void)decrease;
+@end
+
+NS_ASSUME_NONNULL_END
+
+#endif /* KMPOVMSubscriptionCount_h */

KMPObservableViewModelCoreObjC/KMPOVMViewModelScope.h

@@ -9,12 +9,17 @@
 #define KMPOVMViewModelScope_h
 
 #import <Foundation/Foundation.h>
+#import "KMPOVMPublisher.h"
+#import "KMPOVMSubscriptionCount.h"
+
+NS_ASSUME_NONNULL_BEGIN
 
 __attribute__((swift_name("ViewModelScope")))
 @protocol KMPOVMViewModelScope
-- (void)increaseSubscriptionCount;
-- (void)decreaseSubscriptionCount;
-- (void)setSendObjectWillChange:(void (^ _Nonnull)(void))sendObjectWillChange;
+@property (readonly) id<KMPOVMSubscriptionCount> subscriptionCount;
+@property id<KMPOVMPublisher> _Nullable publisher;
 @end
 
+NS_ASSUME_NONNULL_END
+
 #endif /* KMPOVMViewModelScope_h */

KMPObservableViewModelCoreObjC/KMPObservableViewModelCoreObjC.h

@@ -5,4 +5,6 @@
 //  Created by Rick Clephas on 27/11/2022.
 //
 
+#import "KMPOVMPublisher.h"
+#import "KMPOVMSubscriptionCount.h"
 #import "KMPOVMViewModelScope.h"