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Generate an interface from a class

This example shows how a concrete service can generate a matching interface and be consumed through Pure.DI.

using Shouldly;
using Pure.DI;

DI.Setup(nameof(Composition))
    .Bind().To<EmailSender>()
    .Root<App>(nameof(App));

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

app.Provider.ShouldBe("smtp");
app.Result.ShouldBe("sent:ops@contoso.com");

public partial interface IEmailSender;

[GenerateInterface]
public class EmailSender : IEmailSender
{
    public string Provider => "smtp";

    public string Send(string address) => $"sent:{address}";
}

public class App(IEmailSender sender)
{
    public string Provider { get; } = sender.Provider;

    public string Result { get; } = sender.Send("ops@contoso.com");
}
Running this code sample locally 
dotnet --list-sdk
  • Create a net10.0 (or later) console application
dotnet new console -n Sample
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

The example shows how to:

  • Generate an interface from a class
  • Bind the generated contract in Pure.DI
  • Resolve a consumer that depends on the interface
The following partial class will be generated 
partial class Composition
{
  public App App
  {
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    get
    {
      return new App(new EmailSender());
    }
  }

  [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);
      }
    }
  }
}
The following partial class will be generated 
}

Class diagram:

---
 config:
  class:
   hideEmptyMembersBox: true
---
classDiagram
	EmailSender --|> IEmailSender
	Composition ..> App : App App
	App *-- EmailSender : IEmailSender
	namespace Pure.DI.UsageTests.Interfaces.GenerateInterfaceScenario {
		class App {
				<<class>>
			+App(IEmailSender sender)
		}
		class Composition {
		<<partial>>
		+App App
		+ T ResolveᐸTᐳ()
		+ T ResolveᐸTᐳ(object? tag)
		+ object Resolve(Type type)
		+ object Resolve(Type type, object? tag)
		}
		class EmailSender {
				<<class>>
			+EmailSender()
		}
		class IEmailSender {
			<<interface>>
		}
	}
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