scope.md

Scope

The Scoped lifetime ensures that there will be a single instance of the dependency for each scope.

interface IDependency
{
    bool IsDisposed { get; }
}

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

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

interface IService
{
    IDependency Dependency { get; }
}

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

// Implements a session
class Session(Composition composition) : Composition(composition);

class Program(Func<Session> sessionFactory)
{
    public Session CreateSession() => sessionFactory();
}

partial class Composition
{
    void Setup() =>
        DI.Setup(nameof(Composition))
            // This hint indicates to not generate methods such as Resolve
            .Hint(Hint.Resolve, "Off")
            .Bind().As(Scoped).To<Dependency>()

            // Session composition root
            .RootBind<IService>("SessionRoot").To<Service>()

            // Program composition root
            .Root<Program>("ProgramRoot");
}

var composition = new Composition();
var program = composition.ProgramRoot;
        
// Creates session #1
var session1 = program.CreateSession();
var dependency1 = session1.SessionRoot.Dependency;
var dependency12 = session1.SessionRoot.Dependency;
        
// Checks the identity of scoped instances in the same session
dependency1.ShouldBe(dependency12);
        
// Creates session #2
var session2 = program.CreateSession();
var dependency2 = session2.SessionRoot.Dependency;
        
// Checks that the scoped instances are not identical in different sessions
dependency1.ShouldNotBe(dependency2);
        
// Disposes of session #1
session1.Dispose();
// Checks that the scoped instance is finalized
dependency1.IsDisposed.ShouldBeTrue();
        
// Disposes of session #2
session2.Dispose();
// Checks that the scoped instance is finalized
dependency2.IsDisposed.ShouldBeTrue();

The following partial class will be generated:

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

  private Dependency? _scopedDependency36;

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

  internal Composition(Composition parentScope)
  {
    _root = (parentScope ?? throw new ArgumentNullException(nameof(parentScope)))._root;
    _lock = _root._lock;
    _disposables = new object[1];
  }

  public IService SessionRoot
  {
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    get
    {
      if (_scopedDependency36 == null)
      {
          lock (_lock)
          {
              if (_scopedDependency36 == null)
              {
                  _scopedDependency36 = new Dependency();
                  _disposables[_disposeIndex++] = _scopedDependency36;
              }
          }
      }

      return new Service(_scopedDependency36!);
    }
  }

  public Program ProgramRoot
  {
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    get
    {
      var perResolveFunc43 = default(Func<Session>);
      perResolveFunc43 = new Func<Session>(
      [MethodImpl(MethodImplOptions.AggressiveInlining)]
      () =>
      {
          Composition transientComposition2 = this;
          var localValue0 = new Session(transientComposition2);
          return localValue0;
      });
      return new Program(perResolveFunc43!);
    }
  }

  public void Dispose()
  {
    int disposeIndex;
    object[] disposables;
    lock (_lock)
    {
      disposeIndex = _disposeIndex;
      _disposeIndex = 0;
      disposables = _disposables;
      _disposables = new object[1];
      _scopedDependency36 = 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:

classDiagram
	class Composition {
		<<partial>>
		+Program ProgramRoot
		+IService SessionRoot
	}
	Composition --|> IDisposable
	class Session {
		+Session(Composition composition)
	}
	class Program {
		+Program(FuncᐸSessionᐳ sessionFactory)
	}
	Dependency --|> IDependency
	class Dependency {
		+Dependency()
	}
	Service --|> IService
	class Service {
		+Service(IDependency dependency)
	}
	class Composition
	class FuncᐸSessionᐳ
	class IDependency {
		<<interface>>
	}
	class IService {
		<<interface>>
	}
	Session *--  Composition : Composition
	Program o-- "PerResolve" FuncᐸSessionᐳ : FuncᐸSessionᐳ
	Service o-- "Scoped" Dependency : IDependency
	Composition ..> Service : IService SessionRoot
	Composition ..> Program : Program ProgramRoot
	FuncᐸSessionᐳ *--  Session : Session