Blazing fast, minimal but complete dependency injection library for Unity

Reflex is an Dependency Injection framework for Unity. Making your classes independent of its dependencies, granting better separation of concerns. It achieves that by decoupling the usage of an object from its creation. This helps you to follow SOLID’s dependency inversion and single responsibility principles. Making your project more readable, testable and scalable.

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📌 Table Of Contents

• Overview
• Installation
  • Unity Package Manager
  • Open Unity Package Manager
  • Unity Package
• Getting Started
• Execution Order
• Injection Strategy
• Container Hierarrchy
• Scopes
• Bindings
• Resolving
• Callbacks
• Attributes
• Manual Injection
• Extensions
• Debugger
• Settings
• Performance
• Scripting Restrictions
• Support
• License

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👀 Overview

• Fast: ~3x faster than VContainer, ~7x faster than Zenject.
• GC Friendly: ~2x less allocations than VContainer, ~9x less allocations than Zenject.
• AOT Support: Basically there's no runtime Emit, so it works fine on IL2CPP builds. ^[*]
• Contract Table: Allows usages of APIs like container.All<IDisposable>
• Immutable Container: Performant thread safety free of lock plus predictable behavior.

Compatible with the following platforms:

• iOS
• Android
• Windows/Mac/Linux
• PS4/PS5
• Xbox One/S/X and Xbox Series X/S
• WebGL

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💾 Installation

You can install Reflex using any of the following methods:

Unity Package Manager

https://github.com/gustavopsantos/reflex.git?path=/Assets/Reflex/#8.5.0

1. In Unity, open Window → Package Manager.
2. Press the + button, choose "Add package from git URL..."
3. Enter url above and press Add.

Open Unity Package Manager

openupm install com.gustavopsantos.reflex

Unity Package

1. Download the .unitypackage from releases page.
2. Import Reflex.X.X.X.unitypackage

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🚀 Getting Started

1. Install Reflex
2. Create ProjectInstaller.cs with

using Reflex.Core;
using UnityEngine;

public class ProjectInstaller : MonoBehaviour, IInstaller
{
    public void InstallBindings(ContainerBuilder builder)
    {
        builder.AddSingleton("Hello");
    }
}

3. In unity project window
4. Create directory Assets/Resources
5. Select just created Resources dir
6. Right click, Create → Reflex → ProjectScope
7. With just created ProjectScope selected
8. Add ProjectInstaller.cs created at step 2 as a component
9. Create new scene Greet
10. Add Greet to Build Settings → Scenes In Build
11. Create Greeter.cs with

using UnityEngine;
using System.Collections.Generic;
using Reflex.Attributes;

public class Greeter : MonoBehaviour
{
    [Inject] private readonly IEnumerable<string> _strings;

    private void Start()
    {
        Debug.Log(string.Join(" ", _strings));
    }
}

12. Add Greeter.cs to any gameobject in Greet scene
13. Inside Greet scene, create a new empty gameobject named SceneScope and attach SceneScope component
14. Create GreetInstaller.cs with

using Reflex.Core;
using UnityEngine;

public class GreetInstaller : MonoBehaviour, IInstaller
{
    public void InstallBindings(ContainerBuilder builder)
    {
        builder.AddSingleton("World");
    }
}

15. Add GreetInstaller.cs to Greet.unity SceneScope
16. Create new scene Boot
17. Add Boot to Build Settings → Scenes In Build
18. Create Loader.cs with

using Reflex.Core;
using UnityEngine;
using UnityEngine.SceneManagement;

public class Loader : MonoBehaviour
{
    private void Start()
    {
	// If you are loading scenes without addressables
	var scene = SceneManager.LoadScene("Greet", new LoadSceneParameters(LoadSceneMode.Single));
	ReflexSceneManager.PreInstallScene(scene, builder => builder.AddSingleton("Beautiful"));

	// If you are loading scenes with addressables
	Addressables.LoadSceneAsync("Greet", activateOnLoad: false).Completed += handle =>
	{
		ReflexSceneManager.PreInstallScene(handle.Result.Scene, builder => builder.AddSingleton("Beautiful"));
		handle.Result.ActivateAsync();
	};
    }
}

19. Assign it to any gameobject at Boot scene
20. Thats it, hit play while on Boot scene
21. When Greet scene is loaded, there should be 3 instances implementing string contract
22. So when Greeter::Start is called, you should see the following log in the unity console: Hello Beautiful world

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🎬 Execution Order

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🎯 Injection Strategy

Beginning from version 8.0.0, Reflex stops injecting all scenes automatically on Start, to start injecting only scenes with a SceneScope on Awake. This allows users to consume injected dependencies on callbacks such as Awake and OnEnable while giving more granular control on which scenes must be injected or not.

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🌱 Container Hierarchy

Default Behaviour

Reflex's default strategy for creating containers involves initially generating a root project container. For each newly loaded scene, an additional container is created, which always inherits from the root project container. This container hierarchy mirrors the flat hierarchy of Unity scenes. You can see how the structure looks like below:

graph
ProjectContainer --> BootScene
ProjectContainer --> LobbyScene
ProjectContainer --> GameModeOneScene
ProjectContainer --> GameModeTwoScene

Loading

Scene Parent Override

If you want a scene to inherit services from another scene, you can use the ReflexSceneManager::OverrideSceneParentContainer method. This feature provides developers with more granular control over which parent container is used for each newly loaded scene.

// Sample
var bootScene = SceneManager.GetSceneByName("Boot");  
var sessionScene = SceneManager.LoadScene("Session", new LoadSceneParameters(LoadSceneMode.Additive));  
ReflexSceneManager.OverrideSceneParentContainer(scene: sessionScene, parent: bootScene.GetSceneContainer());

By utilizing this API, you can create hierarchical structures such as the one shown below:

graph
ProjectContainer-->BootScene
BootScene-->LobbyScene
LobbyScene-->GameModeOneScene
LobbyScene-->GameModeTwoScene

Loading

1. Please note that it is not possible to override the parent container for the initial scene loaded by Unity.
2. Exercise caution when managing the scene lifecycle with this type of hierarchy. For example, unloading a parent scene before its child scenes can lead to unexpected behavior, as the parent container will be disposed while the child scenes are still active. As a general rule, always unload the scene hierarchy from the bottom up, starting with the child scenes and progressing to the parent scenes.

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📦 Scopes

Container scoping refers to the ability of being able to create a container inheriting the registrations of its parent container while also being able to extend it.

Project Scope

It is root scope. It is created just before first scene opens by relying on [RuntimeInitializeOnLoadMethod(RuntimeInitializeLoadType.BeforeSceneLoad)] To register bindings to it, create a prefab, name it how you wish, the name is not used as a identifier, put it inside any Resources folder, and attach a "ProjectScope" component to it. Then, create your installer as MonoBehaviour and implement IInstaller interface. Remember to attach your installer to the ProjectScope prefab, as ProjectScope searches for every child implementing IInstaller when it's time to create the ProjectScope container. There's a menu item to ease the process: Assets > Create > Reflex > ProjectScope You can create multiple ProjectScope in many different Resources folders across the project, and when its time to create the project container, all active ProjectScope prefabs will be merged, this allow a better separation of concerns if required. Note that ProjectScope prefab is not required, in case Reflex does not find any ProjectScope, an empty root will be created. ProjectScope instance will be disposed once app closes/app quits.

Note that unity does not call OnDestroy deterministically, so rule of thumb is do not rely on injected dependencies on OnDestroy event functions.

Scene Scope

It is scoped from ProjectScope, inheriting all bindings from ProjectScope. It is created and injected before Awake. To register bindings to it, create a gameobject on desired scene, name it "SceneScope", put it as root game object, and attach a "SceneScope" component to it. Then, create your installer as MonoBehaviour and implement IInstaller interface. Remember to attach your installer to your SceneScope gameobject, as SceneScope searches for every child implementing IInstaller when it's time to create the SceneScope container. There's a menu item to ease the process: GameObject > Reflex > Scene Context Remember to have a single SceneScope to avoid undesired behaviour. Note that SceneScope gameobject is required only if you want its scene to be injected, in case Reflex do not find SceneScope, the scene injection will be skipped for that specific scene missing SceneScope. SceneScope instance will be disposed once scene is unloaded.

Note that unity does not call OnDestroy deterministically, so rule of thumb is do not rely on injected dependencies on OnDestroy event functions.

Manual Scoping

using var scopedContainer = parentContainer.Scope(builder =>  
{  
  // Extend your scoped container by adding extra registrations here  
});

🔩 Bindings

AddSingleton (From Type)

ContainerBuilder::AddSingleton(Type concrete, params Type[] contracts)

Adds a deferred object creation based on the type to be constructed and its contracts. The object will be constructed lazily, once first request to resolve any of its contracts is called. Then same object will always be returned. If object implements IDisposable it will be disposed when its parent Container are disposed. There's no need to pass IDisposable as contract to have your object disposed, however, if you want to retrieve all IDisposable by any API Single<TContract>, Resolve<TContract> or All<TContract> then yes, you have to specify it.

AddSingleton (From Value)

ContainerBuilder::AddSingleton(object instance, params Type[] contracts)

Adds an object already constructed by the user to the container as a singleton, everytime the contracts given is asked to be resolved, the same object will be returned. If object implements IDisposable it will be disposed when its parent Container are disposed. There's no need to pass IDisposable as contract to have your object disposed, however, if you want to retrieve all IDisposable by any API Single<TContract>, Resolve<TContract> or All<TContract> then yes, you have to specify it.

AddSingleton (From Factory)

ContainerBuilder::AddSingleton<T>(Func<Container, T> factory, params Type[] contracts)

Adds a deferred object creation based on the given factory and its contracts. The object will be constructed lazily, once first request to resolve any of its contracts is called. The factory will be ran once, and then the same object will always be returned. If object implements IDisposable it will be disposed when its parent Container are disposed. There's no need to pass IDisposable as contract to have your object disposed, however, if you want to retrieve all IDisposable by any API Single<TContract>, Resolve<TContract> or All<TContract> then yes, you have to specify it.

AddTransient (From Type)

ContainerBuilder::AddTransient(Type concrete, params Type[] contracts)

Adds a deferred object creation based on the type to be constructed and its contracts. The object will be constructed lazily, once first request to resolve any of its contracts is called. Then for any request of any contract, a new object will be created, use this carefully. If object implements IDisposable it will be disposed when its parent Container are disposed. There's no need to pass IDisposable as contract to have your object disposed, however, if you want to retrieve all IDisposable by any API Single<TContract>, Resolve<TContract> or All<TContract> then yes, you have to specify it.

AddTransient (From Value)

ContainerBuilder::AddTransient(object instance, params Type[] contracts)

Adds an object already constructed by the user to the container as a transient. It's gonna be returned only on first time it gets resolved, second time an exception will be throw. If object implements IDisposable it will be disposed when its parent Container are disposed. There's no need to pass IDisposable as contract to have your object disposed, however, if you want to retrieve all IDisposable by any API Single<TContract>, Resolve<TContract> or All<TContract> then yes, you have to specify it.

AddTransient (From Factory)

ContainerBuilder::AddTransient(Func<Container, T> factory, params Type[] contracts)

Adds a deferred object creation based on the given factory and its contracts. The object will be constructed lazily, once first request to resolve any of its contracts is called. Then for any request of any contract, a new object will be created, use this carefully. If object created by factory implements IDisposable it will be disposed when its parent Container are disposed. There's no need to pass IDisposable as contract to have your object disposed, however, if you want to retrieve all IDisposable by any API Single<TContract>, Resolve<TContract> or All<TContract> then yes, you have to specify it.

🔍 Resolving

Constructor

If your type is non-mono, and it's going to be created by the container, then the most recommended way to inject dependencies into it its by constructor injection. It's simply as just requesting the contracts you need as following example:

private class Foo
{  
	...
  
	public NumberManager(IInputManager inputManager, IEnumerable<IManager> managers)  
	{  
		...
	}  
}

Note that constructor injection relies on Resolve<TContract> API, so in case there's two objects with IInputManager contract, the last one will be injected.

Attribute

Attribute injection is the way to go for MonoBehaviours. You can use it to inject fields, writeable properties and methods like following:

class Foo : MonoBehaviour  
{  
	[Inject] private readonly IInputManager _inputManager;  
	[Inject] public IEnumerable<IManager> Managers { get; private set; }  
  
	[Inject]  
	private void Inject(IEnumerable<int> numbers) // Method name here does not matter  
	{  
	  ...
	}  
}

Note that attribute injection also works on non-mono classes.

Single

Container::Single<TContract> actually validates that there's a single binding implementing given contract, and returns it. If there's more than one the following exception will be thrown.

InvalidOperationException: Sequence contains more than one element

It's recommended for every binding that you know that there should be a single binding implementing the contract.

Resolve

Container::Single<TContract> runs no validations, and return the last valid object implementing given contract.

All

Container::All<TContract> returns all objects implementing given contract. Example:

private void Documentation_Bindings()  
{  
	var container = new ContainerBuilder("")  
		.AddSingleton(1)  
		.AddSingleton(2)  
		.AddSingleton(3)  
		.Build();  
  
	Debug.Log(string.Join(", ", container.All<int>())); // Prints: 1, 2, 3
}

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🪝 Callbacks

ContainerBuilder::OnContainerBuilt

OnContainerBuilt is a instance callback of ContainerBuilder, it is called once the container is fully built and initialized properly.

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🔖 Attributes

InjectAttribute

Should be used to inject fields, writeable properties and methods like following:

class Foo : MonoBehaviour  
{  
	[Inject] private readonly IInputManager _inputManager;  
	[Inject] public IEnumerable<IManager> Managers { get; private set; }  
  
	[Inject]  
	private void Inject(IEnumerable<int> numbers) // Method name here does not matter  
	{  
	  ...
	}  
}

Note that InjectAttribute also works on non-mono classes.

ReflexConstructorAttribute

Can be placed on constructors, telling reflex which constructor to use when instantiating an object. By default its not required, as usually injected classes have a single constructor, so by default reflex tries to find the constructor with most arguments. But sometimes this can be required if you need more granular control on which construtor reflex should use.

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💉 Manual Injection

If objects (plain old c# objects or unity objects) are created during runtime, theres no way reflex can detect this creation to auto inject the object, this needs to be done manually using one of the following methods:

AttributeInjector::void Inject(object obj, Container container)
// Injects given object fields, properties and methods that was annotated with Inject attribute

ConstructorInjector::object Construct(Type concrete, Container container)
// construct object of given type, using the constructor with most parameters, using given container to pull the constructor arguments

GameObjectInjector::void InjectSingle(GameObject gameObject, Container container)
// Optimized code meant to find injectables (MonoBehaviours) from a given GameObject, to then, inject using AttributeInjector
// This option injects only the first MonoBehaviour found on the given GameObject

GameObjectInjector::void InjectObject(GameObject gameObject, Container container)
// Optimized code meant to find injectables (MonoBehaviours) from a given GameObject, to then, inject using AttributeInjector
// This option injects all MonoBehaviours found on the given GameObject (not recursively, so it does not account for children) 

GameObjectInjector::void InjectRecursive(GameObject gameObject, Container container)
// Optimized code meant to find injectables (MonoBehaviours) from a given GameObject, to then, inject using AttributeInjector
// This option injects all MonoBehaviours found on the given GameObject and its childrens recursively 

GameObjectInjector::void InjectRecursiveMany(List<GameObject> gameObject, Container container)
// Optimized code meant to find injectables (MonoBehaviours) from a given GameObject, to then, inject using AttributeInjector
// This option injects all MonoBehaviours found on the given list of GameObject and its childrens recursively 

Components

An alternative approach is to utilize the GameObjectSelfInjector, which can be attached to a prefab to resolve its dependencies at runtime. Through the inspector, you can select the injection strategy: Single, Object, or Recursive. Each strategy invokes the corresponding method in the GameObjectInjector class.

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🧩 Extensions

// Allows you to get a scene container, allowing you to resolve/inject dependencies in a different way during runtime
SceneExtensions::GetSceneContainer(this Scene scene)
{
    return UnityInjector.ContainersPerScene[scene];
}

// Usage example:
var foo = gameObject.scene.GetSceneContainer().Resolve<IFoo>();

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🐛 Debugger

It can be accessed from menu item Reflex → Debugger.
To enable reflex debug mode you must go to Edit → Project Settings → Player, then in the Other Settings panel, scroll down to Script Compilation → Scripting Define Symbols and add REFLEX_DEBUG. This can be easily achieved by clicking on the bug button at bottom right corner inside Reflex Debugger Window.

Note that debug mode reduces performance and increases memory pressure, so use it wisely.

Legend

Icon	Name	Description
	Name taken from Name property of a Container instance. Scene containers uses scene.name + scene.GetHashCode(), so you can differentiate between two instances of the same opened scene.	Represents a container, containers has a collection of bindings
	Name created from the array of contracts you described your binding.	Represents a binding, bindings has a collection of instances, singleton will have only one instance, transients can have many instances and factories depends on your implementation
	Name taken from Name property of the Type of the concrete object.	Represents a instance, it's the concrete object that were created by the parent binding and it's being injected to consumers

Debugger window allows you to inspect the following:

• Hierarchy of Containers, Bindings and Instances
• Binding Contracts, Kind and Lifetime
• Binding Resolution Count
• Container construction call stack (who created the container)
• Binding construction call stack (who created the binding)
• Instance construction call stack (who resolved the binding making selected instance to be instantiated)

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🪛 Settings

It's a ReflexSettings scriptable object instance, named ReflexSettings that should live inside a Resources folder. It can be created by asset menu item Assets → Create → Reflex → Settings.

Currently, logging verbosity is configured in this file, and default value is set to Info

Non-obligatory to have but projects without it will fallback using default settings

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📊 Performance

Resolving ten thousand times a transient dependency with four levels of chained dependencies. See NestedBenchmarkReflex.cs.

Android + Mono

	GC	Time	GC Ratio	Time Ratio
Reflex	54.7KB	9.3ms	1x	1x
Zenject	512KB	63.2ms	9.36x	6.79x
VContainer	128.9KB	29.8ms	2.35x	3.20x

Android + IL2CPP

	GC	Time	GC Ratio	Time Ratio
Reflex	140.6KB	7.4ms	1x	1x
Zenject	1024KB	23.6ms	7.28x	3.18x
VContainer	257.8KB	9.2ms	1.83x	1.24x

Windows + Mono

	GC	Time	GC Ratio	Time Ratio
Reflex	109.4KB	1.2ms	1x	1x
Zenject	1024KB	9.2ms	9.36x	7.66x
VContainer	257.8KB	3.3ms	2.35x	2.75x

Windows + IL2CPP

	GC	Time	GC Ratio	Time Ratio
Reflex	140.6KB	2.9ms	1x	1x
Zenject	1024KB	9.3ms	7.28x	3.20x
VContainer	257.8KB	5.1ms	1.83x	1.75x

🚫 Scripting Restrictions

If you are taking advantage of reflex to inject IEnumerable<T> in your constructors AND your are building for IL2CPP, you will probably get some exceptions like following:

System.ExecutionEngineException: Attempting to call method 'System.Linq.Enumerable::Cast<ANY-TYPE>' for which no ahead of time (AOT) code was generated.

This happens because compiler does not know at compile time that a specific System.Linq.Enumerable::Cast<T> should be included. And currently Reflex does not implement any type of assembly weaving.

Reflex 4.0.0 had and assembly weaver that was relying on unity UnityEditor.Compilation.CompilationPipeline events and Mono.Cecil. But it was causing conflicts with projects using Burst. So it's being removed temporarly until a definitive solution is found. Most probably we are going to weave assemblies the same way unity is doing for Burst as well.

Temporary workaround example:

class NumberManager
{
    public IEnumerable<int> Numbers { get; }

    public NumberManager(IEnumerable<int> numbers)
    {
        Numbers = numbers;
    }
    
    // https://docs.unity3d.com/Manual/ScriptingRestrictions.html
    [Preserve] private static void UsedOnlyForAOTCodeGeneration()
    {
        Array.Empty<object>().Cast<int>(); // This compiler hint will get rid of: System.ExecutionEngineException: Attempting to call method 'System.Linq.Enumerable::Cast<System.Int32>' for which no ahead of time (AOT) code was generated. 
        throw new Exception("This method is used for AOT code generation only. Do not call it at runtime.");
    }
}

🤝 Support

Ask your questions and participate in discussions regarding Reflex related and dependency injection topics at the Reflex Discord server.

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📜 License

Reflex is distributed under the terms of the MIT License. A complete version of the license is available in the LICENSE file in this repository. Any contribution made to this project will be licensed under the MIT License.