disposable-singleton.md

Disposable singleton

To dispose all created singleton instances, simply dispose the composition instance:

using Shouldly;
using Pure.DI;
using static Pure.DI.Lifetime;

DI.Setup(nameof(Composition))
    // This hint indicates to not generate methods such as Resolve
    .Hint(Hint.Resolve, "Off")
    .Bind().As(Singleton).To<Dependency>()
    .Bind().To<Service>()
    .Root<IService>("Root");

IDependency dependency;
using (var composition = new Composition())
{
    var service = composition.Root;
    dependency = service.Dependency;
}

dependency.IsDisposed.ShouldBeTrue();

interface IDependency
{
    bool IsDisposed { get; }
}

class Dependency : IDependency, IDisposable
{
    public bool IsDisposed { get; private set; }

    public void Dispose() => IsDisposed = true;
}

interface IService
{
    public IDependency Dependency { get; }
}

class Service(IDependency dependency) : IService
{
    public IDependency Dependency { get; } = dependency;
}

Running this code sample locally

• Make sure you have the .NET SDK 9.0 or later is installed

dotnet --list-sdk

• Create a net9.0 (or later) console application

dotnet new console -n Sample

• Add references to NuGet packages
  • Pure.DI
  • Shouldly

dotnet add package Pure.DI
dotnet add package Shouldly

• Copy the example code into the Program.cs file

You are ready to run the example 🚀

dotnet run

A composition class becomes disposable if it creates at least one disposable singleton instance.

The following partial class will be generated:

partial class Composition: IDisposable
{
  private readonly Composition _root;
  private readonly Lock _lock;
  private object[] _disposables;
  private int _disposeIndex;

  private Dependency? _singletonDependency43;

  [OrdinalAttribute(256)]
  public Composition()
  {
    _root = this;
    _lock = new Lock();
    _disposables = new object[1];
  }

  internal Composition(Composition parentScope)
  {
    _root = (parentScope ?? throw new ArgumentNullException(nameof(parentScope)))._root;
    _lock = _root._lock;
    _disposables = parentScope._disposables;
  }

  public IService Root
  {
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    get
    {
      if (_root._singletonDependency43 is null)
      {
        using (_lock.EnterScope())
        {
          if (_root._singletonDependency43 is null)
          {
            _root._singletonDependency43 = new Dependency();
            _root._disposables[_root._disposeIndex++] = _root._singletonDependency43;
          }
        }
      }

      return new Service(_root._singletonDependency43);
    }
  }

  public void Dispose()
  {
    int disposeIndex;
    object[] disposables;
    using (_lock.EnterScope())
    {
      disposeIndex = _disposeIndex;
      _disposeIndex = 0;
      disposables = _disposables;
      _disposables = new object[1];
      _singletonDependency43 = null;
      }

      while (disposeIndex-- > 0)
      {
        switch (disposables[disposeIndex])
        {
          case IDisposable disposableInstance:
            try
            {
              disposableInstance.Dispose();
            }
            catch (Exception exception)
            {
              OnDisposeException(disposableInstance, exception);
            }
            break;
        }
      }
    }

    partial void OnDisposeException<T>(T disposableInstance, Exception exception) where T : IDisposable;
}

Class diagram:

---
 config:
  class:
   hideEmptyMembersBox: true
---
classDiagram
	Composition --|> IDisposable
	Service --|> IService
	Dependency --|> IDependency
	Composition ..> Service : IService Root
	Service o-- "Singleton" Dependency : IDependency
	namespace Pure.DI.UsageTests.Lifetimes.DisposableSingletonScenario {
		class Composition {
		<<partial>>
		+IService Root
		}
		class Dependency {
			+Dependency()
		}
		class IDependency {
			<<interface>>
		}
		class IService {
			<<interface>>
		}
		class Service {
			+Service(IDependency dependency)
		}
	}
	namespace System {
		class IDisposable {
			<<abstract>>
		}
	}

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