Add test for view store state access (#642)

Author: stephencelis

Sources/ComposableArchitecture/ViewStore.swift

@@ -61,6 +61,11 @@ public final class ViewStore<State, Action>: ObservableObject {
   // won't be synthesized automatically. To work around issues on iOS 13 we explicitly declare it.
   public private(set) lazy var objectWillChange = ObservableObjectPublisher()
 
+  /// The current state.
+  public var state: State { self.store.state.value }
+
+  private let store: Store<State, Action>
+  
   /// Initializes a view store from a store.
   ///
   /// - Parameters:
@@ -72,20 +77,13 @@ public final class ViewStore<State, Action>: ObservableObject {
     removeDuplicates isDuplicate: @escaping (State, State) -> Bool
   ) {
     self.publisher = StorePublisher(store.state, removeDuplicates: isDuplicate)
-    self._state = { store.state.value }
-    self._send = store.send
+    self.store = store
     self.viewCancellable = store.state
       .dropFirst()
       .removeDuplicates(by: isDuplicate)
       .sink { [weak self] _ in self?.objectWillChange.send() }
   }
 
-  let _state: () -> State
-  let _send: (Action) -> Void
-
-  /// The current state.
-  public var state: State { _state() }
-
   /// Returns the resulting value of a given key path.
   public subscript<LocalState>(dynamicMember keyPath: KeyPath<State, LocalState>) -> LocalState {
     self.state[keyPath: keyPath]
@@ -101,7 +99,7 @@ public final class ViewStore<State, Action>: ObservableObject {
   ///
   /// - Parameter action: An action.
   public func send(_ action: Action) {
-    self._send(action)
+    self.store.send(action)
   }
 
   /// Derives a binding from the store that prevents direct writes to state and instead sends

Tests/ComposableArchitectureTests/ViewStoreTests.swift

@@ -75,6 +75,28 @@ final class ViewStoreTests: XCTestCase {
     XCTAssertEqual(28, equalityChecks)
     XCTAssertEqual(44, subEqualityChecks)
   }
+
+  func testAccessViewStoreStateInPublisherSink() {
+    let reducer = Reducer<Int, Void, Void> { count, _, _ in
+      count += 1
+      return .none
+    }
+
+    let store = Store(initialState: 0, reducer: reducer, environment: ())
+    let viewStore = ViewStore(store)
+
+    var results: [Int] = []
+
+    viewStore.publisher
+      .sink { _ in results.append(viewStore.state) }
+      .store(in: &self.cancellables)
+
+    viewStore.send(())
+    viewStore.send(())
+    viewStore.send(())
+
+    XCTAssertEqual([0, 1, 2, 3], results)
+  }
 }
 
 private struct State: Equatable {