# Inject Classes

There are different ways to inject classes using dependency injection. Zenject provides constructor, field, property, and method injection.

{% hint style="warning" %}
 **It is recommended to only use Constructor and Method Injection.** [**Read more here**](https://github.com/modesttree/Zenject)
{% endhint %}

## Constructor Injection

Most of your scripts will probably inherit form **`MonoBehaviour`** so you will not be able to use constructor injection. If your class is a service or helper class that does not inherit **`MonoBehaviour`** then you can use constructor injection. 

```csharp
internal class DependencyInjectionExample
{
    private EasyEvents _events;

    public DependencyInjectionExample(EasyEvents events)
    {
        _events = events;
    }
}
```

Zenject dependency Injection will automatically provide an instance of **EasyEvents** into the **`DependencyInjectionExample`** class

{% hint style="info" %}
Zenject will inject dependencies during Unity's**`Awake()`** phase. Recommended to access the injected dependencies in the **`Start()`**method instead of **`Awake()`**
{% endhint %}

## Method Injection

Most of your scripts will probably inherit form **`MonoBehaviour`** so you will not be able to use constructor injection. In that case you will need to use Method injection. There 2 ways that you can use **Method** **Injection.**

### 1. Have a private variable that is assigned via method injection and used throughout your class. Injected only once. 

{% hint style="info" %}
I have named the method **Initialize()** but you can use whatever method name you want. I have seen other people use the naming convention **Constructor()** since it acts like a constructor for classes that inherit from **MonoBehaviour** 
{% endhint %}

```csharp
internal class DependencyInjectionExample : MonoBehaviour
{
    private EasyEvents _events;

    [Inject]
    private void Initialize(EasyEvents events)
    {
        _events = events;
    }
    
    public void AddEvent()
    {
        _events.LoggedIn += OnLoggedIn;
    }

    public void RemoveEvent()
    {
        _events.LoggedIn -= OnLoggedIn;
    }

    private void OnLoggedIn(ILoginSession loginSession)
    {
        Debug.Log($"User {loginSession.LoginSessionId.DisplayName} has logged in");
    }
}
```

### 2. Inject the class into every method that needs. Injected into every class with <mark style="color:blue;">\[Inject]</mark> attribute

```csharp
internal class DependencyInjectionExample : MonoBehaviour
{
    [Inject]
    public void AddEvent(EasyEvents events)
    {
        events.LoggedIn += OnLoggedIn;
    }

    [Inject]
    public void RemoveEvent(EasyEvents events)
    {
        events.LoggedIn -= OnLoggedIn;
    }

    private void OnLoggedIn(ILoginSession loginSession)
    {
        Debug.Log($"User {loginSession.LoginSessionId.DisplayName} has logged in");
    }
    
    [Inject]
    private void AudioSettings(EasyAudio audio)
    {
        audio.AdjustLocalPlayerAudioVolume(25, EasySession.Client);
    }
}
```