Fix change & receive

Sources/TokamakCore/Modifiers/OnChangeModifier.swift

@@ -28,19 +28,17 @@ struct OnChangeModifier<V: Equatable>: ViewModifier {
 
   func body(content: Content) -> some View {
     content
-      .onReceive(Just(value)) { newValue in
-        // TODO: Fix, when @State if working with in a ViewModifier
-        // ignore first call when oldValue == nil. For now old value is always nil
-        if newValue != oldValue {
-          action(oldValue ?? value, newValue)
-        }
-        oldValue = value
-      }
       .onAppear {
         if initial {
           action(value, value)
         }
       }
+      .onReceive(Just(value)) { newValue in
+        if let oldValue, newValue != oldValue {
+          action(oldValue, newValue)
+        }
+        oldValue = value
+      }
   }
 }
 

Sources/TokamakCore/Modifiers/OnReceiveModifier.swift

@@ -18,31 +18,18 @@
 import Foundation
 import OpenCombineShim
 
-private struct OnReceiveModifier<P: Publisher>: ViewModifier where P.Failure == Never {
-  @ObservedObject
-  var cancellableHolder = CancellableHolder()
-
+struct OnReceiveModifier<P: Publisher>: ViewModifier where P.Failure == Never {
   init(publisher: P, action: @escaping (P.Output) -> ()) {
-    cancellableHolder.cancellable = publisher.sink(receiveValue: action)
+    Task {
+      for await value in publisher.values {
+        action(value)
+      }
+    }
   }
 
   func body(content: Content) -> some View {
     content
   }
-
-  // MARK: Types
-
-  final class CancellableHolder: ObservableObject {
-    var cancellable: AnyCancellable? {
-      didSet {
-        oldValue?.cancel()
-      }
-    }
-
-    deinit {
-      cancellable?.cancel()
-    }
-  }
 }
 
 public extension View {

Sources/TokamakDemo/Modifiers/ReceiveChangeDemo.swift

@@ -0,0 +1,49 @@
+// Copyright 2020 Tokamak contributors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+//  Created by Szymon on 24/8/2023.
+//
+
+#if os(WASI) && compiler(>=5.5) && (canImport(Concurrency) || canImport(_Concurrency))
+import TokamakDOM
+
+struct ReceiveChangeDemo: View {
+  @State
+  private var count = 0
+  @State
+  private var count2 = 0
+
+  var body: some View {
+    VStack {
+      Text("Count: \(count)")
+      Text("Count2: \(count2)")
+
+      HStack {
+        Button("Increment") {
+          count += 1
+        }
+        Button("Increment2") {
+          count2 += 1
+        }
+      }
+    }
+    .onChange(of: count) { oldValue, newValue in
+      print("🚺 changed \(oldValue) - \(newValue)")
+    }
+    .onChange(of: count2, initial: true) { oldValue, newValue in
+      print("▶️ init, changed \(oldValue) - \(newValue)")
+    }
+  }
+}
+#endif

Sources/TokamakDemo/TokamakDemo.swift

@@ -134,6 +134,7 @@ struct TokamakDemoView: View {
           Section(header: Text("Modifiers")) {
             NavItem("Shadow", destination: ShadowDemo())
             #if os(WASI) && compiler(>=5.5) && (canImport(Concurrency) || canImport(_Concurrency))
+            NavItem("Receive Change", destination: ReceiveChangeDemo())
             NavItem("Task", destination: TaskDemo())
             #endif
           }

Tests/TokamakTests/ViewReactToDataChangesTests.swift

@@ -23,20 +23,31 @@ class ViewModifierTests: XCTestCase {
     let publisher = PassthroughSubject<String, Never>()
     var receivedValue = ""
 
+    let firstExpectation = XCTestExpectation(description: "First value received from publisher")
+    let secondExpectation = XCTestExpectation(description: "Second value received from publisher")
+
     let contentView = Text("Hello, world!")
       .onReceive(publisher) { value in
         receivedValue = value
+        if receivedValue == "Simulate publisher emitting a first value" {
+          firstExpectation.fulfill()
+        } else if receivedValue == "Simulate publisher emitting a next value" {
+          secondExpectation.fulfill()
+        }
       }
 
     XCTAssertEqual(receivedValue, "")
+    _ = TestFiberRenderer(.root, size: .zero).render(contentView)
 
-    // Simulate publisher emitting a value
-    publisher.send("Testing onReceive")
-    XCTAssertEqual(receivedValue, "Testing onReceive")
+    let fisrPush = "Simulate publisher emitting a first value"
+    publisher.send(fisrPush)
+    wait(for: [firstExpectation], timeout: 1.0)
+    XCTAssertEqual(receivedValue, fisrPush)
 
-    // Simulate publisher emitting a value
-    publisher.send("Second onReceive")
-    XCTAssertEqual(receivedValue, "Second onReceive")
+    let secondPush = "Simulate publisher emitting a next value"
+    publisher.send(secondPush)
+    wait(for: [secondExpectation], timeout: 1.0)
+    XCTAssertEqual(receivedValue, secondPush)
   }
 
   func testOnChangeWithValue() {
@@ -56,14 +67,14 @@ class ViewModifierTests: XCTestCase {
     count = 5
 
     // Re-evaluate the view
-    let reconciler = TestFiberRenderer(.root, size: .zero).render(contentView)
+    _ = TestFiberRenderer(.root, size: .zero).render(contentView)
 
     XCTAssertEqual(count, 5)
     XCTAssertEqual(oldCount, 0)
   }
 
   func testOnChangeWithInitialValue() {
-    var count = 0
+    let count = 0
     var actionFired = false
 
     let contentView = Text("Hello, world!")
@@ -74,12 +85,13 @@ class ViewModifierTests: XCTestCase {
     XCTAssertFalse(actionFired)
 
     // Re-evaluate the view
-    let reconciler = TestFiberRenderer(.root, size: .zero).render(contentView)
+    _ = TestFiberRenderer(.root, size: .zero).render(contentView)
 
     XCTAssertTrue(actionFired)
   }
 
   func testModifierComposition() {
+    let expectation = XCTestExpectation(description: "")
     let publisher = PassthroughSubject<Int, Never>()
     var receivedValue = 0
     var count = 0
@@ -90,19 +102,19 @@ class ViewModifierTests: XCTestCase {
       }
       .onReceive(publisher) { value in
         receivedValue = value
+        expectation.fulfill()
       }
 
     XCTAssertEqual(count, 0)
     XCTAssertEqual(receivedValue, 0)
+    _ = TestFiberRenderer(.root, size: .zero).render(contentView)
 
     // Simulate publisher emitting a value
     publisher.send(10)
     // Simulate a change in value
     count = 5
 
-    // Re-evaluate the view
-    let reconciler = TestFiberRenderer(.root, size: .zero).render(contentView)
-
+    wait(for: [expectation], timeout: 1.0)
     XCTAssertEqual(count, 5)
     XCTAssertEqual(receivedValue, 10)
   }