weak-reference.md

Weak Reference

Demonstrates WeakReference<T> injection, allowing references to objects without preventing garbage collection.

using Shouldly;
using Pure.DI;

DI.Setup(nameof(Composition))
    .Bind<ILargeCache>().To<LargeCache>()
    .Bind<IService>().To<Service>()

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

var composition = new Composition();
var service = composition.MyService;

// Represents a large memory object (e.g., a cache of images or large datasets)
interface ILargeCache;

class LargeCache : ILargeCache;

interface IService;

class Service(WeakReference<ILargeCache> cache) : IService
{
    public ILargeCache? Cache =>
        // Tries to retrieve the target object from the WeakReference.
        // If the object has been collected by the GC, it returns null.
        cache.TryGetTarget(out var value)
            ? value
            : null;
}

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

WeakReference<T> is useful for caching scenarios where you want to allow garbage collection when memory is constrained.

The following partial class will be generated:

partial class Composition
{
  public IService MyService
  {
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    get
    {
      return new Service(new WeakReference<ILargeCache>(new LargeCache()));
    }
  }
}

Class diagram:

---
 config:
  maxTextSize: 2147483647
  maxEdges: 2147483647
  class:
   hideEmptyMembersBox: true
---
classDiagram
	LargeCache --|> ILargeCache
	Service --|> IService
	Composition ..> Service : IService MyService
	Service *--  WeakReferenceᐸILargeCacheᐳ : WeakReferenceᐸILargeCacheᐳ
	WeakReferenceᐸILargeCacheᐳ *--  LargeCache : ILargeCache
	namespace Pure.DI.UsageTests.BCL.WeakReferenceScenario {
		class Composition {
		<<partial>>
		+IService MyService
		}
		class ILargeCache {
			<<interface>>
		}
		class IService {
			<<interface>>
		}
		class LargeCache {
				<<class>>
			+LargeCache()
		}
		class Service {
				<<class>>
			+Service(WeakReferenceᐸILargeCacheᐳ cache)
		}
	}
	namespace System {
		class WeakReferenceᐸILargeCacheᐳ {
				<<class>>
			+WeakReference(ILargeCache target)
		}
	}

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