bind-attribute.md

Bind attribute

BindAttribute lets you bind properties, fields, or methods declared on the bound type.

using Pure.DI;

DI.Setup(nameof(Composition))
    .Bind().As(Lifetime.Singleton).To<DeviceFeatureProvider>()
    .Bind().To<PhotoService>()

    // Composition root
    .Root<IPhotoService>("PhotoService");

var composition = new Composition();
var photoService = composition.PhotoService;
photoService.TakePhotoWithLocation();

interface IGps
{
    void GetLocation();
}

class Gps : IGps
{
    public void GetLocation() => Console.WriteLine("Coordinates: 123, 456");
}

interface ICamera
{
    void Capture();
}

class Camera : ICamera
{
    public void Capture() => Console.WriteLine("Photo captured");
}

class DeviceFeatureProvider
{
    // The [Bind] attribute specifies that the property is a source of dependency
    [Bind] public IGps Gps { get; } = new Gps();

    [Bind] public ICamera Camera { get; } = new Camera();
}

interface IPhotoService
{
    void TakePhotoWithLocation();
}

class PhotoService(IGps gps, Func<ICamera> cameraFactory) : IPhotoService
{
    public void TakePhotoWithLocation()
    {
        gps.GetLocation();
        cameraFactory().Capture();
    }
}

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 a reference to the NuGet package
  • Pure.DI

dotnet add package Pure.DI

• Copy the example code into the Program.cs file

You are ready to run the example 🚀

dotnet run

It applies to instance or static members, including members that return generic types.

The following partial class will be generated:

partial class Composition
{
#if NET9_0_OR_GREATER
  private readonly Lock _lock = new Lock();
#else
  private readonly Object _lock = new Object();
#endif

  private DeviceFeatureProvider? _singletonDeviceFeatureProvider62;

  public IPhotoService PhotoService
  {
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    get
    {
      IGps transientIGps234;
      EnsureDeviceFeatureProviderExists();
      DeviceFeatureProvider localInstance_1182D1277 = _singletonDeviceFeatureProvider62;
      transientIGps234 = localInstance_1182D1277.Gps;
      Func<ICamera> perBlockFunc235 = new Func<ICamera>(
      [MethodImpl(MethodImplOptions.AggressiveInlining)]
      () =>
      {
        ICamera transientICamera237;
        EnsureDeviceFeatureProviderExists();
        DeviceFeatureProvider localInstance_1182D1278 = _singletonDeviceFeatureProvider62;
        transientICamera237 = localInstance_1182D1278.Camera;
        return transientICamera237;
      });
      return new PhotoService(transientIGps234, perBlockFunc235);
      [MethodImpl(MethodImplOptions.AggressiveInlining)]
      void EnsureDeviceFeatureProviderExists()
      {
        if (_singletonDeviceFeatureProvider62 is null)
          lock (_lock)
            if (_singletonDeviceFeatureProvider62 is null)
            {
              _singletonDeviceFeatureProvider62 = new DeviceFeatureProvider();
            }
      }
    }
  }
}

Class diagram:

---
 config:
  maxTextSize: 2147483647
  maxEdges: 2147483647
  class:
   hideEmptyMembersBox: true
---
classDiagram
	PhotoService --|> IPhotoService
	Composition ..> PhotoService : IPhotoService PhotoService
	PhotoService *--  IGps : IGps
	PhotoService o-- "PerBlock" FuncᐸICameraᐳ : FuncᐸICameraᐳ
	ICamera o-- "Singleton" DeviceFeatureProvider : DeviceFeatureProvider
	IGps o-- "Singleton" DeviceFeatureProvider : DeviceFeatureProvider
	FuncᐸICameraᐳ *--  ICamera : ICamera
	namespace Pure.DI.UsageTests.Basics.BindAttributeScenario {
		class Composition {
		<<partial>>
		+IPhotoService PhotoService
		}
		class DeviceFeatureProvider {
				<<class>>
			+DeviceFeatureProvider()
		}
		class ICamera {
				<<interface>>
		}
		class IGps {
				<<interface>>
		}
		class IPhotoService {
			<<interface>>
		}
		class PhotoService {
				<<class>>
			+PhotoService(IGps gps, FuncᐸICameraᐳ cameraFactory)
		}
	}
	namespace System {
		class FuncᐸICameraᐳ {
				<<delegate>>
		}
	}

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