Is it possible to call a function when starting a Unity program?

Question

I was wondering if there is a way in Unity, when I run my program on stage, it starts the function first, I have to add that I want this one function to work no matter what area I am in. a simple start function will not allow it. Not sure if this is possible in Unity?

public void ProgramBegins()
{
    //FIRES FIRST ON ANY SCENE
    //DO STUFF
}

Answer 1

RuntimeInitializeOnLoadMethodAttribute can help you :)

using UnityEngine;

class MyClass
{
    [RuntimeInitializeOnLoadMethod(RuntimeInitializeLoadType.BeforeSceneLoad)]
    static void OnBeforeSceneLoadRuntimeMethod()
    {
        Debug.Log("Before scene loaded");
    }
}

Answer 2

Here you can find the execution order of all functions in unity: http://docs.unity3d.com/Manual/ExecutionOrder.html

Awake - , . GameObject script, Awake. , , .

, . GameObject , , .

Answer 3

prefab _AppStartup, , script AppStartup. AppStartup , , @maZZZu.

AppStartup :

• , .

• ,

  public class AppStartup : MonoBehaviour 
  {
      const int bootSceneNo = 0;
  
      public static bool veryFirstCallInApp =  true;
  
      void Awake ()
      {
          if (veryFirstCallInApp) {
              ProgramBegins ();
              if (Application.loadedLevel != bootSceneNo) {
                  // not the right scene, load boot scene and CU later
                  Application.LoadLevel (bootSceneNo);
                  // return as this scene will be destroyed now
                  return;
              } else {
                  // boot scene stuff goes here
              }
          } else {
              // stuff that must not be done in very first initialisation but afterwards
          }
          InitialiseScene ();
          veryFirstCallInApp = false;
          DestroyObject (gameObject);
      }
  
      void ProgramBegins()
      {
          // code executed only once when the app is started
      }
  
      void InitialiseScene ()
      {
          // code to initialise scene
      }
  }
  

So all you have to do is drag this assembly into each scene manually and give it -100 or something else in the order the script runs. Especially when the project grows and relies on a predetermined flow of the scene, it will save you a lot of time and hassle.