Develop Reference

Initializing a prefab's instance's variable

So I'm currently spawning a instance of a prefab GameObject, and I want to initialize some of its variables. Usually I would use FindObjectOfType, however the objects I want to attach to it don't have a type, and are pretty much just empty GameObjects with a few children. I feel like the answer should be incredibly obvious, but I can't wrap my head around a solution. Any help would be greatly appreciated.
Edit: I forgot to mention that the GameObjects I want to apply to the instance's variables are inactive at the time I want to do so.

If you are instantiating the object then wanting to set the variables, then just spawn the object and grab the reference.
YourScriptHere tmp = Instantiate(yourObject).GetComponent<YourScriptHere>();
tmp.SetTheFieldHereEqualTo = someValue;
If you do not want to just set references to an object you are spawning, can you clarify your question a bit?

Sorry if my question wasn't super clear, but I managed to find a solution. I basically put the objects I want to set as the variables in parent object which is always active, then through the script I get the parent object, and finally I get its first child, which would be the object I wanted in the first place:
GameObject variable;
GameObject variableParent;
private void Start()
{
variableParent = GameObject.Find("variableParentName");
variable = variableParent.transform.GetChild(0).gameObject;
}

How to: Get instance of gameObject

Looking to get an instance of this game object so I can successfully use .enabled to hide it in a scene.
PlayPortalLoginButton loginButton = gameObject.GetComponent<PlayPortalLoginButton>();
Fairly new to C# and I believe I am close to achieving my goal with the line above. What needs changed? Want to understand how to correctly do this.

Here is one way you could find a component on a GameObject in the scene, where "PortalLoginButton" is the name of the GameObject as seen in the editor:
var loginButton = GameObject.Find("PortalLoginButton");
loginButton.enabled = false;
However, GameObject.Find("...") searches the name of every GameObject in the scene, and this is not usually the best way to reference a GameObject since it is not very efficient. So make sure not to use GameObject.Find("...") or similar function calls in the Update() function because it will execute every frame and slow your game down. If the GameObject is not instantiated while the game is running, it is usually better to make a global reference to any GameObject or Component that you use in your script and then drag-and-drop the GameObject with the Component you are looking for into the field in the editor. Alternatively, you can use GameObject.Find("...") in the Start() or Awake() functions to store a reference to the GameObject that you are looking for, so that the search only happens once at the start of your game.
Here is an example of how to store the reference in global field (it will show up in the editor and you can drag-and-drop the GameObject into it). The differences between using a public field vs a private field are explained in the comments (you can decide on using public or private):
// By default, private fields are not viewable in the editor,
// but the [SerializeField] attribute, placed before
// the field declaration, allows them to be visible.
[SerializeField]
private GameObject loginButtonPrivateReference;
// If you need to access loginButton from another script,
// you can make it a public field.
// Public fields are viewable in the editor by default.
public GameObject loginButtonPublicReference;
Here is an example of how you can use GameObject.Find("...") in the Awake() function:
private GameObject loginButton;
private void Awake() {
loginButton = GameObject.Find("PortalLoginButton");
}
If you need to search for GameObjects in your scene by type or by tag name, see the GameObject documentation here for more information. Searching by type is less efficient and searching by tag is more efficient than searching by name because type searches check each component on each GameObject, and tag searches search only an organized GameObject subset.

GameObject button;
void Start() {
button = GameObject.Find ("yourButtom");
}
void SomeEvent() {
button.SetActive(false);
}
I think you have to help to you

There are several ways to get access to a gameObject in a script depending on exactly which gameObject you are trying to get.
If you are trying to access a GameObject of a behavior in the behavior script then simply using gameObject should suffice since that is the gameObject that behavior is attached to.
Accessing a script that is attached to another GameObject is where it can be tricky. For scenes such as a MainMenu, there is nothing wrong with giving it a public reference as an example:
public PlayPortalLoginButton loginButton;
void setLoginState(bool activate) {
loginButton.enabled = activate;
}
With this example you would just drag and drop the gameObject with the PlayPortalLoginButton script on your manager script, the script that would control whether it is enabled or not.
If you need a more modular approach to it for example in a gameplay scene where you are populating objects at run time the approach you can take is:
PlayPortalLoginButton loginButton;
void setLoginState(bool activate) {
if(loginButton == null)
{
loginButton = FindObjectOfType<PlayPortalLoginButton>();
}
// Requires the correct version of .net otherwise you can reuse the check above...
loginButton?.enabled = activate;
}
In the above script if you needed to gameObject of loginButton, now you can access it through loginButton.gameObject.
There are some more examples you could use and other approaches however I feel the above should suffice if for a menu.
I will also mention I am avoiding example of GameObject.Find and GameObject.FindGameObjectsWithTag as those are more prone to error. They will only work if your name or tag are correctly marked, if you rename them for any reason then your scripts will fail to find the Object, and this can cause an issue with troubleshooting.
Using FindObjectOfType, you are less likely to have an error, and if you remove that script type these scripts will populate an error indicating the script no longer exists. When refactoring, if you right click on the behaviors name and use the rename option it will automatically update references to the script throughout your code.

How to delete an object in Unity in ExecuteInEditMode

What I am trying to do
I am trying to have one object with a serialized int that will spawn the number of objects I specify. When I change the number to a lower number, it should obviously delete and destroy the previous ones created.
This is causing an issue, however, do to the way Update works with ExecuteInEditMode, in that it gets executed whenever the scene gets changed, making this much harder.
What I've tried
[ExecuteInEditMode]
public class Floor : MonoBehaviour
{
[SerializeField] GameObject gameObject;
[SerializeField] bool destroy;
private void Update()
{
if (destroy)
{
destroy = !destroy;
gameObject.Destroy();
}
}
}
Unreal Engine used this pattern a lot of having a visible bool that turns itself off and behaves more like a button in the editor, which came in handy. This would allow me to press destroy and destroy the object. Obviously, without the check, it would destroy gameObject, and Update is called again, it will destroy it again and so on.
I thought by added this boolean check, when Update was called again, it wouldn't do anything so the loop would stop, but nope, it continues and gets me an infinite loop.
I've also tried using a Corroutine, but that didn't fix anything.
Is there any way to delete an object in ExecuteInEditMode without causing an infinite loop? Maybe there's a better method than Update that doesn't update when anything in the scene changes?

Try
GameObject.DestroyImmediate(gameObject);
in Edit mode: https://docs.unity3d.com/ScriptReference/Object.DestroyImmediate.html

Use DestroyImmediate() in edit mode since Destroy() is delayed(delayed deconstruction will never be executed in edit mode).
unity docs: https://docs.unity3d.com/ScriptReference/Object.DestroyImmediate.html

Accessing a script from another script at runtime in Unity C#

Like in here, but the difference is that it's supposed to be done from an instantiated prefab, so I can not drag the GameObject, that has the script with the variable I want to access, into this script.
This was working
public ScriptA script;
void Update() {
if (script.varX < 0) {
// . . .
}
}
But now I'm getting "Object reference not set to an instance of an object" error, which I think comes from the fact that the script trying to access ScriptA, is attached to an instantiated prefab.
How do I attach scripts and/or GameObjects at runtime?

Looks like you need to find your script type first, if it already exists in the scene:
public ScriptA script;
void Start()
{
script = GameObject.FindObjectOfType<ScriptA>();
}
void Update()
{
if(script.variable...)
}

You want to use AddComponent, like:
ScriptA script = gameObject.AddComponent<ScriptA>() as ScriptA;
See the docs here:
https://docs.unity3d.com/ScriptReference/GameObject.AddComponent.html

Best way to satify the links is fill the fields in the very next lines after you instantiate, that way you can avoid ugly and expenstive Find* calls (I am assuming the script that does the instancing can be made aware of what the target objects are, after all it knows what and where to instantiate)
Its worth noting that newly instantiated scripts' Awake() method will be called before Instantiate() returns, while its Start() will be called at the start of following frame, this is a major difference between the two calls, so if your instantiated script needs the refectences in Awake() you should either refactor (move stuff to Start()) or use Find* as suggested earlier.

How to randomly generate GameObjects programmatically?

I'd like some help with the following issue. I'm making a simple game where you have a character running and he has to jump over obstacles coming at him.
And I'm currently stuck when it comes to creating GameObjects and randomly generating them within the game scene at run time.
I've written a class to help accomplish this:
using UnityEngine;
using System.Collections;
public class randomObstacles : MonoBehaviour {
public GameObject myCube;
public Vector3 spawnLocation = new Vector3(0,2,0);
// Use this for initialization
void Start () {
GameObject SpawnLocation = (GameObject)Instantiate(myCube, spawnLocation, Quaternion.identity);
}
// Update is called once per frame
void Update () {
}
}
The above code is what I wrote to simply create Objects, one after the other. But when I run the game, it comes up empty -_- !
Can anyone please tell me where am going wrong, and from the look of it my code doesn't seem to do what I am hoping to achieve :(
I've attached the above script into an empty GameObject as I saw in a tutorial from the Unity Community forum, but that did not help either.
(I've looked around and it seems like no one has come across such an issue - I could bee wrong)

It would seem that your myCube variable is the root of your problems, having tested it in a scene of my own. By subsituting
(GameObject)Instantiate(myCube, ...
with
(GameObject)Instantiate(GameObject.CreatePrimitive(PrimitiveType.Cube), ...
I was able to produce a cube at (0,2,0) with no qualms. Perhaps your myCube GameObject is missing a Mesh Renderer, in which case it would appear in the Hierarchy during runtime even though it would not appear visible in Game View. Perhaps you are not assigning it in the Inspector before you run the game, in which case the myCube variable would refer to null and thus not be created. Additionally, though you may be assigning the GameObject you instantiate to SpawnLocation, it is an unused local variable (something MonoDevelop or your code editor should notify you of). Make sure you either provide a reference to a myCube GameObject in the Inspector before runtime or through script referencing to a loaded prefab/GameObject during runtime. It would also be helpful to provide a fallback (say, to PrimitiveType.Cube perhaps?), which will make your code more robust and able to handle errors in referencing should they arise.
Regardless, in order to achieve the functionality you have described, first make sure yo have properly prepared whatever you would desire myCube to be. Also, for future posterity, you may want to initialize your spawnLocation in the Start routine, and assign the variable coordinates by substituting Random.value * yourValueCeiling in for each random coordinate you would like myCube to spawn on. You could even go as far to make a helper method externalized and thus independent from the start routine, such that you will not have to have a hundred instances of a single script to create a hundred instances of what you need; rather, you can call the method through a single script, and save yourself trouble in this way. If you would so appreciate it, here is my implementation of your objective, hope this helps!
using UnityEngine;
using System.Collections;
public class randomObstacles : MonoBehaviour {
public Vector3 spawnLocation;
public GameObject myCube;
// Use this for initialization
void Start () {
if (myCube != true) {
Debug.Log("myCube not set");
myCube = GameObject.CreatePrimitive(PrimitiveType.Cube);
}
if (myCube.renderer.enabled == false) {
Debug.Log("myCube not rendered");
myCube = GameObject.CreatePrimitive(PrimitiveType.Cube);
}
CreateCube();
}
// Update is called once per frame
void Update () {
}
void CreateCube() {
spawnLocation = new Vector3(0, Random.value * 10, 0);
Instantiate(myCube, spawnLocation, Quaternion.identity);
}
}

It may be worth pointing out that you're creating your object in the Start method, which means your code will only run once: from the name of your class, I'd assume you want to create more than one object using this code.
If you move the code into Update you'll create one object per frame, which is most likely too many. My guess would be that you want something like a coroutine that will run on a random interval, and then spawn cubes repeatedly over time, something like this:
void Start () {
StartCoroutine("SpawnObjects");
}
IEnumerator SpawnObjects()
{
while (keepAddingObjects) // a boolean - could just be "true" or could be controlled elsewhere
{
GameObject SpawnLocation = (GameObject)Instantiate(myCube, spawnLocation, Quaternion.identity);
float delay = Random.Range(1f, 5f); // adjust this to set frequency of obstacles
yield return new WaitForSeconds(delay);
}
}

Taken from my own code in a game that auto generate mazes:
public class Cell
{
private GameObject instance;
public void CreateVisual()
{
// Load a GameObject that exist inside the "Resources" folder.
GameObject prefab = (GameObject)Resources.Load("Models/Walls/3W1");
// Create an instance of the prefab
instance = (GameObject)GameObject.Instantiate(prefab);
instance.transform.position = myPosition;
}
}
I think the part you are missing is the Resources.Load() method.