partial-class.md

Partial class

A partial class can contain setup code.

interface IDependency
{
    long Id { get; }
}

class Dependency(long id) : IDependency
{
    public long Id { get; } = id;
}

class Service(
    [Tag("name with id")] string name,
    IDependency dependency1,
    IDependency dependency2)
{
    public string Name { get; } = name;

    public IDependency Dependency1 { get; } = dependency1;

    public IDependency Dependency2 { get; } = dependency2;
}

// The partial class is also useful for specifying access modifiers to the generated class
public partial class Composition
{
    private readonly string _serviceName = "";
    private long _id;

    // Customizable constructor
    public Composition(string serviceName)
        : this()
    {
        _serviceName = serviceName;
    }

    private long GenerateId() => Interlocked.Increment(ref _id);

    // In fact, this method will not be called at runtime
    [Conditional("DI")]
    void Setup() =>
        DI.Setup()
            .Bind<IDependency>().To<Dependency>()
            .Bind<long>().To(_ => GenerateId())
            .Bind<string>("name with id").To(
                _ => $"{_serviceName}_{GenerateId()}")
            .Root<Service>(
                "Root",
                kind: RootKinds.Internal);
}

var composition = new Composition("Abc");
var service = composition.Root;

service.Dependency1.Id.ShouldBe(1);
service.Dependency2.Id.ShouldBe(2);
service.Name.ShouldBe("Abc_3");

The partial class is also useful for specifying access modifiers to the generated class.

The following partial class will be generated:

partial class Composition
{
  private readonly Composition _root;

  [OrdinalAttribute(20)]
  public Composition()
  {
    _root = this;
  }

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

  internal Service Root
  {
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    get
    {
      long transientInt645 = GenerateId();
      long transientInt644 = GenerateId();
      string transientString1 = $"{_serviceName}_{GenerateId()}";
      return new Service(transientString1, new Dependency(transientInt645), new Dependency(transientInt644));
    }
  }

  [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)
  {
    var index = (int)(_bucketSize * ((uint)RuntimeHelpers.GetHashCode(type) % 1));
    ref var pair = ref _buckets[index];
    return 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 (pair.Key == type)
      {
        return pair.Value.Resolve(this);
      }
    }

    throw new InvalidOperationException($"{CannotResolveMessage} {OfTypeMessage} {type}.");
  }

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

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

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

  static Composition()
  {
    var valResolver_0000 = new Resolver_0000();
    Resolver<Service>.Value = valResolver_0000;
    _buckets = Buckets<Type, IResolver<Composition, object>>.Create(
      1,
      out _bucketSize,
      new Pair<Type, IResolver<Composition, object>>[1]
      {
         new Pair<Type, IResolver<Composition, object>>(typeof(Service), 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 InvalidOperationException($"{CannotResolveMessage}{OfTypeMessage}{typeof(T)}.");
    }

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

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

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

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

Class diagram:

classDiagram
	class Composition {
		<<partial>>
		+Service Root
		+ T ResolveᐸTᐳ()
		+ T ResolveᐸTᐳ(object? tag)
		+ object Resolve(Type type)
		+ object Resolve(Type type, object? tag)
	}
	class Service {
		+Service(String name, IDependency dependency1, IDependency dependency2)
	}
	Dependency --|> IDependency
	class Dependency {
		+Dependency(Int64 id)
	}
	class Int64
	class String
	class IDependency {
		<<interface>>
	}
	Service *--  String : "name with id"  String
	Service *-- "2 " Dependency : IDependency
	Composition ..> Service : Service Root
	Dependency *--  Int64 : Int64

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