inheritance-of-compositions.md

Inheritance of compositions

Demonstrates how composition classes can inherit from each other, allowing reuse of bindings and composition roots across multiple related compositions.

using Shouldly;
using Pure.DI;
using static Pure.DI.CompositionKind;

var composition = new Composition();
var app = composition.App;

// The base composition provides common infrastructure,
// such as database access, that can be shared across different parts of the application.
class Infrastructure
{
    // The 'Internal' kind indicates that this setup is intended
    // to be inherited and does not produce a public API on its own.
    private static void Setup() =>
        DI.Setup(kind: Internal)
            .Bind<IDatabase>().To<SqlDatabase>();
}

// The main composition inherits the infrastructure configuration
// and defines the application-specific dependencies.
partial class Composition : Infrastructure
{
    private void Setup() =>
        DI.Setup()
            .Bind<IUserManager>().To<UserManager>()
            .Root<App>(nameof(App));
}

interface IDatabase;

class SqlDatabase : IDatabase;

interface IUserManager;

class UserManager(IDatabase database) : IUserManager;

partial class App(IUserManager userManager)
{
    public IUserManager UserManager { get; } = userManager;
}

Running this code sample locally

• Make sure you have the .NET SDK 10.0 or later installed

dotnet --list-sdk

• Create a net10.0 (or later) console application

dotnet new console -n Sample

• Add references to the 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

Note

Composition inheritance provides a way to share common bindings while still allowing each derived composition to add its own specific bindings.

The following partial class will be generated:

partial class Composition
{
  public App App
  {
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    get
    {
      return new App(new UserManager(new SqlDatabase()));
    }
  }

  [MethodImpl(MethodImplOptions.AggressiveInlining)]
  public T Resolve<T>()
  {
    return Resolver<T>.Value.Resolve(this);
  }

  [MethodImpl(MethodImplOptions.AggressiveInlining)]
  public T Resolve<T>(object? tag)
  {
    return Resolver<T>.Value.ResolveByTag(this, tag);
  }

  [MethodImpl(MethodImplOptions.AggressiveInlining)]
  public object Resolve(Type type)
  {
    #if NETCOREAPP3_0_OR_GREATER
    var index = (int)(_bucketSize * (((uint)type.TypeHandle.GetHashCode()) % 1));
    #else
    var index = (int)(_bucketSize * (((uint)RuntimeHelpers.GetHashCode(type)) % 1));
    #endif
    ref var pair = ref _buckets[index];
    return Object.ReferenceEquals(pair.Key, type) ? pair.Value.Resolve(this) : Resolve(type, index);
  }

  [MethodImpl(MethodImplOptions.NoInlining)]
  private object Resolve(Type type, int index)
  {
    var finish = index + _bucketSize;
    while (++index < finish)
    {
      ref var pair = ref _buckets[index];
      if (Object.ReferenceEquals(pair.Key, type))
      {
        return pair.Value.Resolve(this);
      }
    }

    throw new CannotResolveException($"{CannotResolveMessage} {OfTypeMessage} {type}.", type, null);
  }

  [MethodImpl(MethodImplOptions.AggressiveInlining)]
  public object Resolve(Type type, object? tag)
  {
    #if NETCOREAPP3_0_OR_GREATER
    var index = (int)(_bucketSize * (((uint)type.TypeHandle.GetHashCode()) % 1));
    #else
    var index = (int)(_bucketSize * (((uint)RuntimeHelpers.GetHashCode(type)) % 1));
    #endif
    ref var pair = ref _buckets[index];
    return Object.ReferenceEquals(pair.Key, type) ? pair.Value.ResolveByTag(this, tag) : Resolve(type, tag, index);
  }

  [MethodImpl(MethodImplOptions.NoInlining)]
  private object Resolve(Type type, object? tag, int index)
  {
    var finish = index + _bucketSize;
    while (++index < finish)
    {
      ref var pair = ref _buckets[index];
      if (Object.ReferenceEquals(pair.Key, type))
      {
        return pair.Value.ResolveByTag(this, tag);
      }
    }

    throw new CannotResolveException($"{CannotResolveMessage} \"{tag}\" {OfTypeMessage} {type}.", type, tag);
  }

  private readonly static uint _bucketSize;
  private readonly static Pair<IResolver<Composition, object>>[] _buckets;

  static Composition()
  {
    var valResolver_0000 = new Resolver_0000();
    Resolver<App>.Value = valResolver_0000;
    _buckets = Buckets<IResolver<Composition, object>>.Create(
      1,
      out _bucketSize,
      new Pair<IResolver<Composition, object>>[1]
      {
         new Pair<IResolver<Composition, object>>(typeof(App), valResolver_0000)
      });
  }

  private const string CannotResolveMessage = "Cannot resolve composition root ";
  private const string OfTypeMessage = "of type ";

  private class Resolver<T>: IResolver<Composition, T>
  {
    public static IResolver<Composition, T> Value = new Resolver<T>();

    public virtual T Resolve(Composition composite)
    {
      throw new CannotResolveException($"{CannotResolveMessage}{OfTypeMessage}{typeof(T)}.", typeof(T), null);
    }

    public virtual T ResolveByTag(Composition composite, object tag)
    {
      throw new CannotResolveException($"{CannotResolveMessage}\"{tag}\" {OfTypeMessage}{typeof(T)}.", typeof(T), tag);
    }
  }

  private sealed class Resolver_0000: Resolver<App>
  {
    public override App Resolve(Composition composition)
    {
      return composition.App;
    }

    public override App ResolveByTag(Composition composition, object tag)
    {
      switch (tag)
      {
        case null:
          return composition.App;

        default:
          return base.ResolveByTag(composition, tag);
      }
    }
  }
}