AManagerClass

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Revision as of 00:13, 1 January 2006 by Aarku (Talk | contribs)

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Author: Keli Hlodversson (freyr)

Contents

Description

The following snippet shows how to add a static property called instance that will automatically find an instance of the class in the scene and return it.

This is useful for managers and other behaviours that only have one instance in the scene and need to be accessed from other classes, as it avoids having each class to keep a reference to the manager object.

Hint: A nice place to put game managers in a scene hierarchy is to create an empty game object called Managers and attach all manager behaviours to it.

Usage

Use the code example as a template when creating a manager-type script. Remember to replace all occurrences of AManager with the name of your class.

C# - AManager.cs

<csharp> using UnityEngine;

using System.Collections; 

/// AManager is a singleton.
/// To avoid having to manually link an instance to every class that needs it, it has a static property called
/// instance, so other objects that need to access it can just call:
///        AManager.instance.DoSomeThing();
///
public class AManager : MonoBehaviour {
   // s_Instance is used to cache the instance found in the scene so we don't have to look it up every time.
   private static AManager s_Instance = null;

   // This defines a static instance property that attempts to find the manager object in the scene and
   // returns it to the caller.
   public static AManager instance {
       get {
           if (s_Instance == null) {
               // This is where the magic happens.
               //  FindObjectOfType(...) returns the first AManager object in the scene.
               s_Instance =  FindObjectOfType(typeof (AManager)) as AManager;
               if (s_Instance == null)
                   Debug.Log ("Could not locate an AManager object. \
                                       You have to have exactly one AManager in the scene.");
           }
           
           return s_Instance;
       }
   }
   
   void Awake() {
       s_Instance = this;
   }
   
   // Add the rest of the code here...
   public void DoSomeThing() {
       Debug.Log("Doing something now", this);
   }
 
}

</csharp>

Boo - AManager.boo

I haven't tested that one btw... so please fix it if you find any errors -- Keli <boo>

import UnityEngine

class AManager (MonoBehaviour) :
"""
AManager is a singleton.
To avoid having to manually link an instance to every class that needs it, it has a static property called
instance, so other objects that need to access it can just call:
       AManager.instance.DoSomeThing()
"""

   # s_Instance is used to cache the instance found in the scene so we don't have to look it up every time.
   private static s_Instance as AManager

   #This defines a static instance property that attempts to find the manager object in the scene and
   # returns it to the caller.
   public static instance :
       get :
           if s_Instance == null :
               # This is where the magic happens.
               #  FindObjectOfType(...) returns the first AManager object in the scene.
               s_Instance =  FindObjectOfType(AManager) 
               if s_Instance == null:
                   Debug.Log ("Could not locate an AManager object. \
                                       You have to have exactly one AManager in the scene.")
           
           return s_Instance

   # Add the rest of the code here...
   def DoSomeThing() :
       Debug.Log("Doing something now", self)

</boo>

Javascript - AManager.js

Note: Unity Javascript does not have a way to declare properties, so the instance property has been replaced with a static variable that gets initialised upon start. This also means that one can not be sure that instance has been initialised if it is accessed during initialisation.

<javascript>

/// AManager is a singleton.
/// To avoid having to manually link an instance to every class that needs it, it has a static variabe called
/// instance, so other objects that need to access it can just call:
///        AManager.instance.DoSomeThing();
///
static var instance : AManager;

// This is where the magic happens.
//  FindObjectOfType(...) returns the first AManager object in the scene.
instance =  FindObjectOfType(AManager);
if (instance == null)
    Debug.Log ("Could not locate an AManager object. \
                    You have to have exactly one AManager in the scene.");
// Add the rest of the code here...
function DoSomeThing() {
    Debug.Log("Doing something now", this);
}

</javascript>

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