Nanoject - MonoBehaviours

What it is

Nanoject MonoBehaviours is an extension for the Nanoject dependency injection solution. It provides extension methods for declaring and injecting MonoBehaviours from the currently open scene in Nanoject's DependencyContext. Since this is not needed in every project it is not part of Nanoject itself.

Installation

In order to install this package to your Unity project, open Packages\manifest.json and add the following dependencies:

"dependencies" : {
    "com.ancientlightstudios.nanoject": "https://github.com/derkork/nanoject-unity.git#3.0.0"
    "com.ancientlightstudios.nanoject-monobehaviours": "https://github.com/derkork/nanoject-unity-monobehaviours.git#2.0.0"
}

Unity currently does not support transitive dependency management for Git, so you will have to enter both URLs.

Basic Usage

Use the DeclareMonoBehavioursFromScene extension method on DependencyContext to scan the current scene for suitable MonoBehaviours and declare them:

// new context
var context = new DependencyContext();

// declare the objects that you want to fetch from the scene
context.DeclareMonoBehavioursFromScene<MyMonoBehaviour>();
context.DeclareMonoBehavioursFromScene<MyOtherMonoBehaviour>();

// declare the objects that need references from the scene
context.Declare<MyService>();

context.Resolve();

How can I ...

Fetch a specific object from the scene if I have multiple of them?

In case you use Unity's GUI system you might want to fetch references to buttons, etc. You can do this by using a qualifier. The qualifier is the object's name in the scene hierarchy. For example if you have two buttons named nextButton and previousButton in your scene hierarchy and want to inject them into a service that should handle the clicks, you can do it like this:

// declare all buttons from the scene using their name as qualifier.
context.DeclareMonoBehavioursFromSceneQualified<Button>();

// then in your service just reference them:
public class UIService {
    public UIService(
        [Qualifier("nextButton")] Button nextButton,
        [Qualifier("previousButton")] Button previousButton) {
        // use the buttons somehow.
    }
}

Inject dependencies into my MonoBehaviours?

MonoBehaviours are managed by Unity, so constructor injection does not work for them. In order to have dependencies injected into your MonoBehaviours you can add a method that is annotated with the LateInit attribute:

public class MyBehaviour : MonoBehaviour {
    private MyService _myService;

    [LateInit]
    // the function must take all dependencies as arguments
    public void SetUp(MyService myService)
    {
        _myService = myService;
    } 
}

This method will be called when the context is resolved. You can also use qualifiers. For example if you want to reference the nextButton and previousButton from the previous example, you could do it like this:

public class MyUIBehaviour : MonoBehaviour {
    private Button _nextButton;
    private Button _previousButton;

    [LateInit]
    public void SetUp(
            [Qualifier("nextButton")] Button nextButton,
            [Qualifier("previousButton")] Button previousButton)
    {
        _nextButton = nextButton;
        _previousButton = previousButton;
    } 
}

Note however, that usually it is easier to wire up MonoBehaviours directly in the scene. The approach shown above is useful if you instantiate your behaviours dynamically from prefabs and cannot wire them up in the scene beforehand.