Baked dependency injection for Unity.

This is a tiny dependency injection framework for Unity, that uses Mono.Cecil to weave generated assemblies and add baked factories and injection methods. This allows injection to work without using reflection making it faster and able to work in AOT compilation, like IL2CPP.

This is still experimental and should not be used in production.

How it works

Using Mono.Cecil it hooks up to unity's CompilationPipeline . When an assembly file is created all classes that have a constructor or fields marked with the Inject attribute will have new methods injected (weaved) that resolve all field and parameters using the Dependency injection container. Each assembly also has a generated master method that has the attribute InitializeOnLoadMethodAttribute or RuntimeInitializeOnLoadMethodAttribute. That method is then called by unity and all weaved methods are registered in the ContainerDatabase and later utilized.

Installation

This uses Unity's package system. The add it you a project it should be added to a folder BakedInject in the Packages folder.

Alternative editing the package manifest located in Packages folder like this:

{
    "dependencies": {
        "baked-inject": "https://github.com/simeonradivoev/BakedInject.git"
    }
}

Usage

The API is very similar to other dependency injection frameworks, with a few catches. Check out Zenject or Ninject

Here is an example usage:

var container = new Container();

//bind instance
container.Bind("Test");

//waved classes can have their field and constructor injected.
container.Bind<BakedClass>().AsSingle();

//use with non weaved class with an empty constructor.
container.BindNew<NonBakedClass>().AsSingle();

//use for non weaved classes using a factory.
container
.Bind<INonBakedClass>()
.AsSingle()
.FromFactory(c => new NonBakedClass2(c.Resolve<string>()));

var bakedClass = container.Resolve<BakedClass>();

All weaved constructors and injection methods are registered in the ContainerDatabase class. It can also be used to manually register factories and injectors if one wants to.

Catches:

Constructors

To instantiate classes they need to have a constructor with the attribute [Inject]. Otherwise they need to be explicitly created by a factory method or passed by instance. Private and public constructors can be injected.

public class TestInjection
{
    public string test;

    [Inject]
    public TestInjection(string test)
    {
        this.test = test;
    }
}

Fields

To inject a field, that field needs to have the [Inject] attribute. Private and public fields can be injected.

public class TestInjection
{
    [Inject]
    public string test;
}

Notes

If you really, really, really want reflection it can be enabled by a script define ENABLE_REFLECT_INJECTION. Then reflection will be used as a fallback

Here is an example weaved master method that registers factories and injectors, de-compiled using JetBrains dotPeek.

using BakedInject;
using Scenes.Scripts;
using UnityEngine;

namespace Injection
{
  public class Baker
  {
    [RuntimeInitializeOnLoadMethod]
    private static void BakeInjection()
    {
      ContainerDatabase.Register<TestInjection2>(new ContainerDatabase.Factory(TestInjection2.TestInjection2FactoryMethod));
      ContainerDatabase.Register<TestInjection>(new ContainerDatabase.Injector(TestInjection.TestInjectionInjectionMethod));
    }
  }
}