Impl AsyncReactiveProperty.ToString, Add State

src/UniTask.NetCoreTests/AsyncReactivePropertyTest.cs

@@ -51,6 +51,67 @@ namespace NetCoreTests
 
             ar.Should().BeEquivalentTo(new[] { 100, 100, 100, 131, 191 });
         }
+
+        [Fact]
+        public async Task StateIteration()
+        {
+            var rp = new State<int>(99);
+            var setter = rp.GetSetter();
+
+            var f = await rp.FirstAsync();
+            f.Should().Be(99);
+
+            var array = rp.Take(5).ToArrayAsync();
+
+            setter(100);
+            setter(100);
+            setter(100);
+            setter(131);
+
+            var ar = await array;
+
+            ar.Should().BeEquivalentTo(new[] { 99, 100, 100, 100, 131 });
+        }
+
+        [Fact]
+        public async Task StateWithoutCurrent()
+        {
+            var rp = new State<int>(99);
+            var setter = rp.GetSetter();
+
+            var array = rp.WithoutCurrent().Take(5).ToArrayAsync();
+            setter(100);
+            setter(100);
+            setter(100);
+            setter(131);
+            setter(191);
+
+            var ar = await array;
+
+            ar.Should().BeEquivalentTo(new[] { 100, 100, 100, 131, 191 });
+        }
+
+
+
+        [Fact]
+        public void StateFromEnumeration()
+        {
+            var rp = new AsyncReactiveProperty<int>(10);
+
+            var state = rp.ToState(CancellationToken.None);
+
+            rp.Value = 10;
+            state.Value.Should().Be(10);
+
+            rp.Value = 20;
+            state.Value.Should().Be(20);
+
+            state.Dispose();
+
+            rp.Value = 30;
+            state.Value.Should().Be(20);
+        }
+
     }
 
 

src/UniTask/Assets/Plugins/UniTask/Runtime/AsyncReactiveProperty.cs

@@ -59,6 +59,24 @@ namespace Cysharp.Threading.Tasks
             triggerEvent.SetCompleted();
         }
 
+        public static implicit operator T(AsyncReactiveProperty<T> value)
+        {
+            return value.Value;
+        }
+
+        public override string ToString()
+        {
+            if (isValueType) return latestValue.ToString();
+            return latestValue?.ToString();
+        }
+
+        static bool isValueType;
+
+        static AsyncReactiveProperty()
+        {
+            isValueType = typeof(T).IsValueType;
+        }
+
         class WithoutCurrentEnumerable : IUniTaskAsyncEnumerable<T>
         {
             readonly AsyncReactiveProperty<T> parent;
@@ -156,4 +174,231 @@ namespace Cysharp.Threading.Tasks
             }
         }
     }
-}
+
+    public class State<T> : IReadOnlyAsyncReactiveProperty<T>, IDisposable
+    {
+        TriggerEvent<T> triggerEvent;
+
+        T latestValue;
+
+        Action<T> setter;
+        IUniTaskAsyncEnumerator<T> enumerator;
+
+        public T Value
+        {
+            get
+            {
+                return latestValue;
+            }
+        }
+
+        public State(T value)
+        {
+            this.latestValue = value;
+            this.triggerEvent = default;
+        }
+
+        public State(T initialValue, IUniTaskAsyncEnumerable<T> source, CancellationToken cancellationToken)
+        {
+            latestValue = initialValue;
+            ConsumeEnumerator(source, cancellationToken).Forget();
+        }
+
+        public State(IUniTaskAsyncEnumerable<T> source, CancellationToken cancellationToken)
+        {
+            ConsumeEnumerator(source, cancellationToken).Forget();
+        }
+
+        async UniTaskVoid ConsumeEnumerator(IUniTaskAsyncEnumerable<T> source, CancellationToken cancellationToken)
+        {
+            enumerator = source.GetAsyncEnumerator(cancellationToken);
+            try
+            {
+                while (await enumerator.MoveNextAsync())
+                {
+                    SetValue(enumerator.Current);
+                }
+            }
+            finally
+            {
+                await enumerator.DisposeAsync();
+                enumerator = null;
+            }
+        }
+
+        public Action<T> GetSetter()
+        {
+            if (enumerator != null)
+            {
+                throw new InvalidOperationException("Can not get setter when create from IUniTaskAsyncEnumerable source.");
+            }
+
+            if (setter != null)
+            {
+                throw new InvalidOperationException("GetSetter can only call once.");
+            }
+
+            setter = SetValue;
+            return setter;
+        }
+
+        void SetValue(T value)
+        {
+            this.latestValue = value;
+            triggerEvent.SetResult(value);
+        }
+
+        public IUniTaskAsyncEnumerable<T> WithoutCurrent()
+        {
+            return new WithoutCurrentEnumerable(this);
+        }
+
+        public IUniTaskAsyncEnumerator<T> GetAsyncEnumerator(CancellationToken cancellationToken)
+        {
+            return new Enumerator(this, cancellationToken, true);
+        }
+
+        public void Dispose()
+        {
+            if (enumerator != null)
+            {
+                enumerator.DisposeAsync().Forget();
+            }
+
+            triggerEvent.SetCompleted();
+        }
+
+        public static implicit operator State<T>(T value)
+        {
+            return new State<T>(value);
+        }
+
+        public static implicit operator T(State<T> value)
+        {
+            return value.Value;
+        }
+
+        public override string ToString()
+        {
+            if (isValueType) return latestValue.ToString();
+            return latestValue?.ToString();
+        }
+
+        static bool isValueType;
+
+        static State()
+        {
+            isValueType = typeof(T).IsValueType;
+        }
+
+        class WithoutCurrentEnumerable : IUniTaskAsyncEnumerable<T>
+        {
+            readonly State<T> parent;
+
+            public WithoutCurrentEnumerable(State<T> parent)
+            {
+                this.parent = parent;
+            }
+
+            public IUniTaskAsyncEnumerator<T> GetAsyncEnumerator(CancellationToken cancellationToken = default)
+            {
+                return new Enumerator(parent, cancellationToken, false);
+            }
+        }
+
+        sealed class Enumerator : MoveNextSource, IUniTaskAsyncEnumerator<T>, ITriggerHandler<T>
+        {
+            static Action<object> cancellationCallback = CancellationCallback;
+
+            readonly State<T> parent;
+            readonly CancellationToken cancellationToken;
+            readonly CancellationTokenRegistration cancellationTokenRegistration;
+            T value;
+            bool isDisposed;
+            bool firstCall;
+
+            public Enumerator(State<T> parent, CancellationToken cancellationToken, bool publishCurrentValue)
+            {
+                this.parent = parent;
+                this.cancellationToken = cancellationToken;
+                this.firstCall = publishCurrentValue;
+
+                parent.triggerEvent.Add(this);
+                TaskTracker.TrackActiveTask(this, 3);
+
+                if (cancellationToken.CanBeCanceled)
+                {
+                    cancellationTokenRegistration = cancellationToken.RegisterWithoutCaptureExecutionContext(cancellationCallback, this);
+                }
+            }
+
+            public T Current => value;
+
+            public UniTask<bool> MoveNextAsync()
+            {
+                // raise latest value on first call.
+                if (firstCall)
+                {
+                    firstCall = false;
+                    value = parent.Value;
+                    return CompletedTasks.True;
+                }
+
+                completionSource.Reset();
+                return new UniTask<bool>(this, completionSource.Version);
+            }
+
+            public UniTask DisposeAsync()
+            {
+                if (!isDisposed)
+                {
+                    isDisposed = true;
+                    TaskTracker.RemoveTracking(this);
+                    completionSource.TrySetCanceled(cancellationToken);
+                    parent.triggerEvent.Remove(this);
+                }
+                return default;
+            }
+
+            public void OnNext(T value)
+            {
+                this.value = value;
+                completionSource.TrySetResult(true);
+            }
+
+            public void OnCanceled(CancellationToken cancellationToken)
+            {
+                DisposeAsync().Forget();
+            }
+
+            public void OnCompleted()
+            {
+                completionSource.TrySetResult(false);
+            }
+
+            public void OnError(Exception ex)
+            {
+                completionSource.TrySetException(ex);
+            }
+
+            static void CancellationCallback(object state)
+            {
+                var self = (Enumerator)state;
+                self.DisposeAsync().Forget();
+            }
+        }
+    }
+
+    public static class StateExtensions
+    {
+        public static State<T> ToState<T>(this IUniTaskAsyncEnumerable<T> source, CancellationToken cancellationToken)
+        {
+            return new State<T>(source, cancellationToken);
+        }
+
+        public static State<T> ToState<T>(this IUniTaskAsyncEnumerable<T> source, T initialValue, CancellationToken cancellationToken)
+        {
+            return new State<T>(initialValue, source, cancellationToken);
+        }
+    }
+}