required-properties-or-fields.md

Required properties or fields

All properties or fields marked with the required keyword automatically become injected dependencies.

using Shouldly;
using Pure.DI;

DI.Setup(nameof(Composition))
    .Arg<string>("name")
    .Bind<IDependency>().To<Dependency>()
    .Bind<IService>().To<Service>()

    // Composition root
    .Root<IService>("Root");

var composition = new Composition(name: "My Service");
var service = composition.Root;
service.Dependency.ShouldBeOfType<Dependency>();
service.Name.ShouldBe("My Service");

interface IDependency;

class Dependency : IDependency;

interface IService
{
    string Name { get; }

    IDependency Dependency { get; }
}

class Service : IService
{
    public required string ServiceNameField;

    public string Name => ServiceNameField;

    // The required property will be injected automatically
    // without additional effort
    public required IDependency Dependency { get; init; }
}

Running this code sample locally

• Make sure you have the .NET SDK 9.0 or later is installed

dotnet --list-sdk

• Create a net9.0 (or later) console application

dotnet new console -n Sample

• Add references to 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

The following partial class will be generated:

partial class Composition
{
  private readonly Composition _root;

  private readonly string _argName;

  [OrdinalAttribute(128)]
  public Composition(string name)
  {
    _argName = name ?? throw new ArgumentNullException(nameof(name));
    _root = this;
  }

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

  public IService Root
  {
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    get
    {
      return new Service()
      {
        ServiceNameField = _argName,
        Dependency = new Dependency()
      };
    }
  }
}

Class diagram:

---
 config:
  class:
   hideEmptyMembersBox: true
---
classDiagram
	Service --|> IService
	Dependency --|> IDependency
	Composition ..> Service : IService Root
	Service o-- String : Argument "name"
	Service *--  Dependency : IDependency
	namespace Pure.DI.UsageTests.Basics.RequiredPropertiesOrFieldsScenario {
		class Composition {
		<<partial>>
		+IService Root
		}
		class Dependency {
			+Dependency()
		}
		class IDependency {
			<<interface>>
		}
		class IService {
			<<interface>>
		}
		class Service {
			+Service()
			+String ServiceNameField
			+IDependency Dependency
		}
	}
	namespace System {
		class String {
		}
	}

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