Add ViewModelCancellable to manage cancellation/clear logic

Author: rickclephas

KMPObservableViewModelCore/ObservableViewModel.swift

@@ -34,9 +34,13 @@ public final class ObservableViewModel<VM: ViewModel>: ObservableObject, Hashabl
     /// The observed `ViewModel`.
     public let viewModel: VM
 
+    /// Holds a strong reference to the cancellable
+    private let cancellable: AnyCancellable
+    
     internal init(_ viewModel: VM) {
         objectWillChange = viewModel.viewModelWillChange
         self.viewModel = viewModel
+        cancellable = ViewModelCancellable.get(for: viewModel)
     }
 
     public static func == (lhs: ObservableViewModel<VM>, rhs: ObservableViewModel<VM>) -> Bool {

KMPObservableViewModelCore/ObservableViewModelPublisher.swift

@@ -13,13 +13,12 @@ public final class ObservableViewModelPublisher: Combine.Publisher, KMPObservabl
     public typealias Output = Void
     public typealias Failure = Never
 
-    internal weak var viewModel: (any ViewModel)?
+    internal let cancellable = ViewModelCancellable()
 
     private let publisher: ObservableObjectPublisher
     private let subscriptionCount: any SubscriptionCount
 
     internal init(_ viewModel: any ViewModel) {
-        self.viewModel = viewModel
         self.publisher = viewModel.objectWillChange
         self.subscriptionCount = viewModel.viewModelScope.subscriptionCount
     }
@@ -32,14 +31,6 @@ public final class ObservableViewModelPublisher: Combine.Publisher, KMPObservabl
     public func send() {
         publisher.send()
     }
-    
-    deinit {
-        guard let viewModel else { return }
-        if let cancellable = viewModel as? Cancellable {
-            cancellable.cancel()
-        }
-        viewModel.clear()
-    }
 }
 
 /// Subscriber for `ObservableViewModelPublisher` that creates `ObservableViewModelSubscription`s.

KMPObservableViewModelCore/ViewModelCancellable.swift

@@ -0,0 +1,37 @@
+//
+//  ViewModelCancellable.swift
+//  KMPObservableViewModel
+//
+//  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 func get(_ viewModel: any ViewModel) -> AnyCancellable {
+        guard didInit else {
+            let cancellable = AnyCancellable {
+                if let cancellable = viewModel as? Cancellable {
+                    cancellable.cancel()
+                }
+                viewModel.clear()
+            }
+            self.cancellable = cancellable
+            didInit = true
+            return cancellable
+        }
+        guard let cancellable = self.cancellable else {
+            fatalError("ObservableViewModel for \(viewModel) has been deallocated")
+        }
+        return cancellable
+    }
+    
+    static func get(for viewModel: any ViewModel) -> AnyCancellable {
+        viewModel.viewModelWillChange.cancellable.get(viewModel)
+    }
+}