custom-universal-attribute.md

Custom universal attribute

A combined attribute can supply tag, ordinal, and type metadata. Each registration method can take an optional argument index (default is 0) that specifies where to read the metadata.

using Shouldly;
using Pure.DI;

DI.Setup(nameof(PersonComposition))
    .TagAttribute<InjectAttribute<TT>>()
    .OrdinalAttribute<InjectAttribute<TT>>(1)
    .TypeAttribute<InjectAttribute<TT>>()
    .Arg<int>("personId")
    .Bind().To(() => new Uri("https://github.com/DevTeam/Pure.DI"))
    .Bind("NikName").To(() => "Nik")
    .Bind().To<Person>()

    // Composition root
    .Root<IPerson>("Person");

var composition = new PersonComposition(personId: 123);
var person = composition.Person;
person.ToString().ShouldBe("123 Nik https://github.com/DevTeam/Pure.DI");

[AttributeUsage(
    AttributeTargets.Constructor
    | AttributeTargets.Method
    | AttributeTargets.Parameter
    | AttributeTargets.Property
    | AttributeTargets.Field)]
class InjectAttribute<T>(object? tag = null, int ordinal = 0) : Attribute;

interface IPerson;

class Person([Inject<string>("NikName")] string name) : IPerson
{
    private object? _state;

    [Inject<int>(ordinal: 1)] internal object Id = "";

    public void Initialize([Inject<Uri>] object state) =>
        _state = state;

    public override string ToString() => $"{Id} {name} {_state}";
}

dotnet --list-sdk

dotnet new console -n Sample

dotnet add package Pure.DI
dotnet add package Shouldly

dotnet run

partial class PersonComposition
{
  private readonly int _argPersonId;

  [OrdinalAttribute(128)]
  public PersonComposition(int personId)
  {
    _argPersonId = personId;
  }

  public IPerson Person
  {
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    get
    {
      string transientString = "Nik";
      Uri transientUri = new Uri("https://github.com/DevTeam/Pure.DI");
      var transientPerson = new Person(transientString);
      transientPerson.Initialize(transientUri);
      transientPerson.Id = _argPersonId;
      return transientPerson;
    }
  }
}

Class diagram:

---
 config:
  class:
   hideEmptyMembersBox: true
---
classDiagram
	Uri --|> IEquatableᐸUriᐳ
	Uri --|> IFormattable
	Uri --|> ISpanFormattable
	Uri --|> ISerializable
	Person --|> IPerson
	PersonComposition ..> Person : IPerson Person
	Person o-- Int32 : Argument "personId"
	Person *-- Uri : Uri
	Person *-- String : "NikName" String
	namespace Pure.DI.UsageTests.Attributes.CustomUniversalAttributeScenario {
		class IPerson {
			<<interface>>
		}
		class Person {
				<<class>>
			+Person(String name)
			~Object Id
			+Initialize(Object state) : Void
		}
		class PersonComposition {
		<<partial>>
		+IPerson Person
		}
	}
	namespace System {
		class IEquatableᐸUriᐳ {
			<<interface>>
		}
		class IFormattable {
			<<interface>>
		}
		class Int32 {
				<<struct>>
		}
		class ISpanFormattable {
			<<interface>>
		}
		class String {
				<<class>>
		}
		class Uri {
				<<class>>
		}
	}
	namespace System.Runtime.Serialization {
		class ISerializable {
			<<interface>>
		}
	}

See also:

• Custom attributes