exposed-roots-with-tags.md

Exposed roots with tags

Composition roots from other assemblies or projects can be used as a source of bindings. When you add a binding to a composition from another assembly or project, the roots of the composition with the RootKind.Exposed type will be used in the bindings automatically. For example, in some assembly a composition is defined as:

public partial class CompositionWithTagsInOtherProject
{
    private static void Setup() =>
        DI.Setup()
            .Bind().As(Lifetime.Singleton).To<MyDependency>()
            .Bind("Some tag").To<MyService>()
            .Root<IMyService>("MyService", "Some tag", RootKinds.Exposed);
}

Use this when a library exposes ready-made composition roots that must be reused in another composition.

using Pure.DI;
using static Pure.DI.Lifetime;
using OtherAssembly;

DI.Setup(nameof(Composition))
    // Binds to exposed composition roots from other project
    .Bind().As(Singleton).To<CompositionWithTagsInOtherProject>()
    .Root<Program>("Program");

var composition = new Composition();
var program = composition.Program;
program.DoSomething();

partial class Program([Tag("Some tag")] IMyService myService)
{
    public void DoSomething() => myService.DoSomething();
}

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

Limitations: exposed roots create an integration contract between assemblies; tag names and root contracts should be versioned carefully. See also: Tags, Exposed roots.

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 OtherAssembly.CompositionWithTagsInOtherProject? _singletonCompositionWithTagsInOtherProject62;

  public Program Program
  {
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    get
    {
      OtherAssembly.IMyService transientIMyService53;
      if (_singletonCompositionWithTagsInOtherProject62 is null)
        lock (_lock)
          if (_singletonCompositionWithTagsInOtherProject62 is null)
          {
            _singletonCompositionWithTagsInOtherProject62 = new OtherAssembly.CompositionWithTagsInOtherProject();
          }

      OtherAssembly.CompositionWithTagsInOtherProject localInstance_1182D1275 = _singletonCompositionWithTagsInOtherProject62;
      transientIMyService53 = localInstance_1182D1275.MyService;
      return new Program(transientIMyService53);
    }
  }
}