SetActive = false on previous instantiated prefab

Question

I am using the following code to create a line of prefabs

 {
  
  public GameObject myPrefab;
  
  Vector3 lastPosition = new Vector3(0,2,0);
  Vector3 offsetVector = new Vector3(0,0,-3);
 
  void Update()
  {
      if(Input.GetKeyDown (KeyCode.Space))
      {
      GameObject myPrefabInstance = GameObject.Instantiate(myPrefab, lastPosition + offsetVector, Quaternion.identity);
      lastPosition = myPrefabInstance.transform.position;
      }
  }
 }

This works great and gives me a nice even row of prefabs. However I want the player to be able to adjust the position of each prefab once it is placed and have an arrow key move script attached to the parent prefab. Of course this means that currently all the prefabs move in unison. How do I disable the previous prefab (perhaps with SetActive = false) once the space bar is pressed and the next prefab is placed. Currently I only want the player to be able to move each prefab once.

Thanks for any suggestions.

Answer 1

Answer by metalted · Jul 01, 2019 at 09:08 PM

You could save the myPrefabInstance as a global GameObject. Each time the Space bar is pressed down, the variable will be overwritten to the newly created gameobject. You then use your movement script on that saved gameobject. When the space bar is pressed again, the new gameobject is assigned to the variable and can be controlled using your script.

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Answer 2

Answer by Jrobson · Jul 02, 2019 at 04:37 PM

@metalted OK, bear with me, I'm a relative noob. I get what you're saying in principle but haven't been able to find an example of this by searching "save prefab instance as global GameObject". Is there another way to phrase this that will help me find some pointers? Thanks.

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metalted · Jul 02, 2019 at 08:59 PM 0

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@Jrobson Ofcourse! So if I understand correctly, you want to create a prefab, let the player control that prefab and then create another prefab, control that one etc... Right now you are creating a GameObject myPrefabInstance inside the if(..$$anonymous$$eyDown..) statement. This means that the so called "scope" of this GameObject can not go outside of the if statement. It is also not available in the rest of the class, like in the other functions. This is what called a "local variable". Local variables are declared inside a function and are only used inside that function.

Then there are the global variables. They are declared inside the class but OUTSIDE of a function. This means that the variable is available to all the functions inside the script. It can even be available outside the script. You can use the "Access level modifiers" for that. You probably seen the public and private keywords. Public variables are accessible from any script, but only if you have a reference to that script.

 Wallet wallet = new Wallet();
 Debug.Log(wallet.money);
 //the money variable has to be declared public for this to be possible

The private variables can only be accessed from within the script. This is used for protection so people can't alter them directly. This is sometimes combined with a function to get and set the variable. This is called "Encapsulation". It not only makes sure the variable gets changed the right way, it also gives user a nice way to interact with your script.

Then there are protected variables, those can only be access by the script they are in AND the script that inherit from that class. "Inheritance" is also something very interesting to look at.

Static variables are a whole different things, but very straightforward its a variable accessible from any script anywhere without a reference to it.

Okay so that enough information for a "relative noob!" Lets get back to the question. If you save the GameObject myPrefabInstance outside of your function, so a global variable like GameObject myPrefab, you can access it later to apply movement to it. Right now, when the key is pressed the gameobject is declared inside the if statement and the next frame it is gone. So when you "Save the prefab instance as global gameobject", it means to assign the newly created gameobject ( a copy from your prefab ) , to the global variable ( a GameObject variable that is inside your class but outside of any function ). After you assign it you could pass it into a function to move it, or apply movement directly by using gameObject.transform.Translate() (or something). I hope this gives you an idea.

metalted · Jul 02, 2019 at 09:02 PM 0

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If you want to start coding quickly, I suggest going through the book "Headfirst C#" or "Headfirst Java". Its both Object Oriented Program$$anonymous$$g. It $$anonymous$$ches basic stuff like variables and types and modifiers to advanced topics like interfaces, polymorphism, inheritance etc etc. I really had fun reading it and doing it, cause there are a lot of exercises and puzzles in there too!

SetActive = false on previous instantiated prefab

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