Variables are data / variables stored as Scriptable Objects. Because Variables are stored as Scriptable Objects they are not part of any scene, but could be instead be seen as part of a global shared game state. Variables are also designed to make it easy to inject (via the Unity Inspector) to your MonoBehaviours.
It is possible to attach an event to a Variable that gets raised when its updated. This makes it possible to write more data-driven code.
It is also possible to attach another event to a Variable that also gets raised when a Variable is changed, but that contains both the old and the new value of the Variable. Unity Atoms generates Pairs (a simple struct) for Atoms containing 2 variables of the same type for this purpose.
You can also add pre change transformers to a Variable. A pre change transformer is an AtomFunction that takes the value type of the Variable, performs some logic, and returns a new value of the same type. It's called on `OnEnable` as well as before setting a new Value of a Variable. An example of a pre change transformer is `ClampInt`, an `IntIntFunction` that clamps the Variable's value between two values.
Exactly the same as Variables, but can not be changed via script and therefore does not contain the change events that Variables does. The idea is to use Constants for for example tags instead of hard coding tags in your scripts.
References are values that can be toggled between `Use Value`, `Use Constant`, `Use Variable` or `Use Variable Instancer` via the Unity Inspector. When a Reference is set to `Use Value` it functions exactly like a regular serialized variable in a MonoBehaviour script. However, when it is set to `Use Variable` or `Use Constant` it uses a Variable or a Constant. When it's set to `Use Variable Instancer` you can drag and drop a Variable Instancer of the correct type.
This is a MonoBehaviour that takes a base Variable and makes an in memory copy of it `OnEnable`. This is particular useful when working with prefabs that is going to be instantiated at runtime. For example, when creating an enemy prefab you can use an `IntVariableInstancer` that creates an in memory copy of the enemy's health that you then can use in your scripts on the enemy prefab (using References). You can also give it a reference to a List or a Collection. If that is done the instancer will add the in memory Variable on Start to the List / Collection and then remove it OnDestroy.
An event is a thing that happens in the game that others can listen / subscribe to. Events in Unity Atoms are also Scriptable Objects that lives outside of a specific scene. It is possible to raise an Event from the Unity Inspector for debugging purposes.
### Pair Events
Like Event, but for pairs. Pairs are simple structs containing 2 variables of the same type, used for example in Variables' Changed With History Event.
Event References are events that can be toggled between `Use Event`, `Use Event Instancer`, `Use Variable` or `Use Variable Instancer` via the Unity Inspector. When an Event Reference is set to `Use Event` it functions exactly like a regular serialized Event in a MonoBehaviour script. When it is set to `Use Event Instancer` you can drag and drop an Event Instancer whos Event the Event Reference will use. When it is set to `Use Variable` it is going to use the Event associated with the Variable's Changed event. When it's set to `Use Variable Instancer` you can drag and drop a Variable Instancer of the correct type and it will use its associated Changed event.
This is a MonoBehaviour that takes a base Event and makes an in memory copy of it `OnEnable`. This is particular useful when working with prefabs that is going to be instantiated at runtime, for example when working with Mono Hooks on your prefabs.
Like Event Instancer, but for pairs. Pairs are simple structs containing 2 variables of the same type, used for example in Variables' Changed With History Event.
A Listener listens / observes / subscribes to an event reference and raises / invokes zero to many responses to that Event Reference. Listeners are MonoBehaviours and lives in a scene. See below for more information on the type of responses there are.
### Pair Event Reference Listeners
Like Event Reference Listeners, but for pairs. Pairs are simple structs containing 2 variables of the same type, used for example in Variables' Changed With History Event.
### Event Reference Listeners
Like Event Reference Listeners, but are using a regular Event instead of an Event Reference. This makes more sense in listeners observing for example Collections (see more info below).
A Responses are raised by a Listener in Response to an event. Responses can live both in the scene as [UnityEvents](https://docs.unity3d.com/ScriptReference/Events.UnityEvent.html) or outside the scene as a Scriptable Object in the shape of an Action.
Like Actions, but for pairs. Pairs are simple structs containing 2 variables of the same type, used for example in Variables' Changed With History Event.
Collections stores multiple values. For all collections in Unity Atoms there is the possibility to add Events for when the following:
- For when an item is added.
- For when an item is removed.
- For when the collection is cleared.
### Value Lists
A Value List is an array of values that is stored as a Scriptable Object.
### Lists
A List is an array of Variables that is stored as a Scriptable Object. The Variables can be different types since it's using `AtomBaseVariable`.
### Collections
A collection is a set of Variables associated with a StringReference key and is stored as a Scriptable Object. The Variables can be different types since it's using `AtomBaseVariable`.
