Why i need to declare a variable that have the same name of class and script? - unity3d

Question

public class CanvasManager : MonoBehaviour
{
public static CanvasManager Instance; // = lobby
[SerializeField]
private LobbyFunction _lobbyFunction;
public LobbyFunction LobbyFunction
{
get { return _lobbyFunction; }
}
...
below is one of the reference
private void Start()
{
GameObject lobbyCanvasGO = CanvasManager.Instance.LobbyFunction.gameObject;
...
I am confused that is it necessary to have the same name of canvasmanager that it is declared , and why there is no error when I sayCanvasManager.Instance.LobbyFunction ,it made me confused since LobbyFunction is belonged to CanvasManager, not Instance.
Finally , sometimes ,
private LobbyFunction _lobbyFunction;
private LobbyFunction LobbyFunction
{
get { return _lobbyFunction; }
}
Sometimes,
private LobbyFunction _lobbyFunction;
public LobbyFunction LobbyFunction
{
get { return _lobbyFunction; }
}
Thanks for your patience reading this, and your help would be greatly appreciated, thanks!

Answer 1

Your class is named CanvasManager, but you cannot statically access it right away.
You created a static member variable in CanvasManager, which holds a reference to a CanvasManager. This is called the singleton pattern.
You can only access static members without a class instance. But in the case of singletons, you create a single instance of the class (usually assigned in Start() or in getInstance() (lazy) after checking if it exists) which you can then access statically through "Instance".
Now, Instance is a static variable holding a reference to a single instance of CanvasManager. So, you can then access non-static members and functions of CanvasManager, if you access "Instance".
Think about it like this:
CanvasManager local_instance = new CanvasManager();
local_instance.non_static_member = value; // this works
CanvasManager.static_member = value; // this works
CanvasManager.non_static_member = value; // won't work.
And now one step further, you access the instance via CanvasManager.Instance.*
CanvasManager.Instance.non_static_member = value; // works!
Explanation of static vs non-static:
normal variables:
Variables needs memory. So usually you create 5 instances of CanvasManager and each instance can have different values. Because each instance reserves memory for each Variable. But if you want to change one, you need to explicitly talk to that instance. You could manage them in a List or by having multiple variables in Code like manager1, manager2...
Think of it as books, where each copy can be modified (write notes into it)
static variables
If you create a static variable, the memory is reserved once for the Class. You can then directly get/set this static variable from anywhere in Code without the need of a Reference to an instance.
Think of it as an online blog, where changes are applied for everyone, being accessible from everywhere. The text exists once in the blog database.
Singletons:
If you only want a single CanvasManager and not 5, you could attach it to any GameObject and access it. But every other script needs a reference, like public CanvasManager my_manager which you need to assign in inspector. As an alterantive, you could use
GameObject.Find("CanvasManagerObject").getComponent<CanvasManager>()
in each script... If only there was a better way to access this CanvasManager from everywhere...
The singleton pattern allows you to get a reference to a single, nonstatic instance of the CanvasManager, while it doesn't even need a GameObject it can attach to.
Naming
You are talking about "it has to have the same name" - this is not true. You can name the instance whatever you like. CanvasManager.MyCustomlyNamedInstance would work too. But the MyCustomlyNamedInstance must be a static variable in the CanvasManager class, or any other class. You could have a GameManager that manages your instances, so GameManager.MyCanvasManagerInstance would work too.