generic-root-arguments.md

Generic root arguments

Demonstrates how to pass type arguments as parameters to generic composition roots.

using Shouldly;
using Pure.DI;

DI.Setup(nameof(Composition))
    .RootArg<TT>("model")
    .Bind<IPresenter<TT>>().To<Presenter<TT>>()

    // Composition root
    .Root<IPresenter<TT>>("GetPresenter");

var composition = new Composition();

// The "model" argument is passed to the composition root
// and then injected into the "Presenter" class
var presenter = composition.GetPresenter<string>(model: "Hello World");

presenter.Model.ShouldBe("Hello World");

interface IPresenter<out T>
{
    T? Model { get; }
}

class Presenter<T> : IPresenter<T>
{
    // The Dependency attribute specifies to perform an injection
    [Dependency]
    public void Present(T model) =>
        Model = model;

    public T? Model { get; private set; }
}

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 references to the 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

Note

Generic root arguments enable flexible type parameterization while maintaining compile-time type safety.

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

  [MethodImpl(MethodImplOptions.AggressiveInlining)]
  public IPresenter<T1> GetPresenter<T1>(T1 model)
  {
    if (model is null) throw new ArgumentNullException(nameof(model));
    var transientPresenter523 = new Presenter<T1>();
    transientPresenter523.Present(model);
    return transientPresenter523;
  }
}

Class diagram:

---
 config:
  maxTextSize: 2147483647
  maxEdges: 2147483647
  class:
   hideEmptyMembersBox: true
---
classDiagram
	PresenterᐸT1ᐳ --|> IPresenterᐸT1ᐳ
	Composition ..> PresenterᐸT1ᐳ : IPresenterᐸT1ᐳ GetPresenterᐸT1ᐳ(T1 model)
	PresenterᐸT1ᐳ o-- T1 : Argument "model"
	namespace Pure.DI.UsageTests.Generics.GenericRootArgScenario {
		class Composition {
		<<partial>>
		+IPresenterᐸT1ᐳ GetPresenterᐸT1ᐳ(T1 model)
		}
		class IPresenterᐸT1ᐳ {
			<<interface>>
		}
		class PresenterᐸT1ᐳ {
				<<class>>
			+Presenter()
			+Present(T1 model) : Void
		}
	}

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