Add DisposableBag

src/R3/Disposable.cs

@@ -17,6 +17,11 @@ public static void AddTo(this IDisposable disposable, ref DisposableBuilder buil
         builder.Add(disposable);
     }
 
+    public static void AddTo(this IDisposable disposable, ref DisposableBag bag)
+    {
+        bag.Add(disposable);
+    }
+
     public static void AddTo(this IDisposable disposable, ICollection<IDisposable> disposables)
     {
         disposables.Add(disposable);

src/R3/DisposableBag.cs

@@ -0,0 +1,53 @@
+namespace R3;
+
+public struct DisposableBag : IDisposable
+{
+    IDisposable[]? items;
+    bool isDisposed;
+    int count;
+
+    public DisposableBag(int capacity)
+    {
+        items = new IDisposable[capacity];
+    }
+
+    public void Add(IDisposable item)
+    {
+        if (isDisposed)
+        {
+            item.Dispose();
+            return;
+        }
+
+        if (items == null)
+        {
+            items = new IDisposable[4];
+        }
+        else if (count == items.Length)
+        {
+            Array.Resize(ref items, count * 2);
+        }
+
+        items[count++] = item;
+    }
+
+    public void Clear()
+    {
+        if (items != null)
+        {
+            for (int i = 0; i < count; i++)
+            {
+                items[i]?.Dispose();
+            }
+
+            items = null;
+            count = 0;
+        }
+    }
+
+    public void Dispose()
+    {
+        Clear();
+        isDisposed = true;
+    }
+}

src/R3/ObservableSubscribeExtensions.cs

@@ -7,7 +7,7 @@ public static class ObservableSubscribeExtensions
     [DebuggerStepThrough]
     public static IDisposable Subscribe<T>(this Observable<T> source)
     {
-        return source.Subscribe(NopObserver<T>.Instance);
+        return source.Subscribe(new NopObserver<T>());
     }
 
     [DebuggerStepThrough]
@@ -52,9 +52,7 @@ public static IDisposable Subscribe<T, TState>(this Observable<T> source, TState
 [DebuggerStepThrough]
 internal sealed class NopObserver<T> : Observer<T>
 {
-    public static readonly NopObserver<T> Instance = new();
-
-    private NopObserver()
+    public NopObserver()
     {
     }
 

tests/R3.Tests/DisposableBagTest.cs

@@ -0,0 +1,32 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace R3.Tests;
+
+public class DisposableBagTest
+{
+    [Fact]
+    public void Test()
+    {
+        var bag = new DisposableBag();
+
+        var disposed = new bool[6];
+
+        var subject = new Subject<int>();
+        subject.Do(onDispose: () => disposed[0] = true).Subscribe().AddTo(ref bag);
+        subject.Do(onDispose: () => disposed[1] = true).Subscribe().AddTo(ref bag);
+        subject.Do(onDispose: () => disposed[2] = true).Subscribe().AddTo(ref bag);
+        subject.Do(onDispose: () => disposed[3] = true).Subscribe().AddTo(ref bag);
+        subject.Do(onDispose: () => disposed[4] = true).Subscribe().AddTo(ref bag);
+        subject.Do(onDispose: () => disposed[5] = true).Subscribe().AddTo(ref bag);
+
+        disposed.Should().Equal([false, false, false, false, false, false]);
+
+        bag.Dispose();
+
+        disposed.Should().Equal([true, true, true, true, true, true]);
+    }
+}