How to maintain reference to object instantiate at runtime in Unity

Question

I need to instantiate an object at runtime, where the number of objects are based on a txt file (number of lines). All objects need to be clickable (onClick() event) and when they are pressed a tooltip must appear. Tooltips are specific ( Object1 -> Tooltip1, Object2 -> Tooltip2). Tooltips are just a Panel and they consist in some other Panels and Buttons. One of these create a new Panel. Also these Panel are specific (Tooltip1 -> Panel1 and so on). I create a prefab for each of three objects.

So, Object1 - onClick() -> Tooltip1 - onClick() -> Panel1. At runtime.

How can I keep reference of an object create at runtime?

My first solution:

Create a Empty object and assign a script to it with a public variable (Object prefab).

Instantiate Object prefab:

for (int i = 0; i < numberOfObject; i++)
{
   var instance = Instantiate(m_ObjectPrefab);
   instance.name = "Object_" + m_nameObject[i];

Instantiate one Tooltip for each Object:

    var instancePanelTooltip = Instantiate(m_panelTooltipPrefab, m_canvas.transform);
    instancePanelTooltip.name = "Panel_Tooltip_" + m_nameObject[i];

Instantiate one Panel for each Tooltip:

   var instancePanel = Instantiate(m_panelPrefab, m_canvas.transform);
   instancePanel.name = "Panel_" + m_nameObject[i];
   instancePanel.SetActive(false);
   instancePanelTooltip.SetActive(false);

Add event handler for Object

    DetectClickOnObject scriptDetectClickPanelTooltip = instance.AddComponent<DetectClickOnObject>();
    scriptDetectClickPanelTooltip.SetTooltip(instancePanelTooltip);

Add event handler for button on Tooltip

    DetectClickOnObject scriptDetectClickPanel = buttonOpenPanel.AddComponent<DetectClickOnObject>();
    scriptDetectClickPanel.SetPanel(instancePanel);
}

Issue with this solution:

I will instantiate 3 object (Object, Tooltip, Panel) for each line of file. For Object it is okay, but it is not with Tooltip and Panel, because only one Tooltip is active among all (same for Panel).
I just avoid the problem of reference because I create in the same place all objects (one for each element), but what can I do if I need to get access to Tooltip2 or Panel3 without a reference (I am trying to avoid Find and similar).

Conclusion of the first solution: Solution is working, but I think there is a better way of doing that (avoid create so much object and keep reference in the right way).

My second solution (guidelines):

I am trying to create a class to keep reference of all object create at runtime.
I want to create an instance of Object for each lines, but I want just one Tooltip and Panel for all Object and changing properties according to Object clicked. So Object is create at runtime, but Tooltip and Panel are already in the scene but not active.
I need a Register Event Manager to add onClick() event at runtime on Objects and it need to handle properties to be set on Tooltip and Panel based on clicked Object.

Problems with second solution: Referring to 1) I tried to follow that, but I ended up with nothing. I am lost between singleton, static and something else. Referring to 2) I think it can be easy, I just need to cut away some of the first solution. Referring to 3) I can not do more if I do not have a class reference manager.

What I am looking for:

Is first solution so bad? If I look at code I am disgusted by it, it is far away from elegance (or something similar).
Can you suggest me how can I keep track of reference create at runtime with a Reference Manager? And how use it?

@Behnam Sattar suggestion: As DataModell class,

public class DataModelPOI
{
    public string m_namePOI { get; private set; }
    public string m_locationPOI { get; private set; }
    public Vector2d m_positionPOI { get; private set; }

    public GameObject m_gameObject_POI;
    public GameObject m_gameObjectTooltip;
    public GameObject m_gameObjectPanel;

    public DataModelPOI(string namePOI, string locationPOI, Vector2d positionPOI)
    {
        this.m_namePOI = namePOI;
        this.m_locationPOI = locationPOI;
        this.m_positionPOI = positionPOI;
    }
}

As DataManager,

public class POIManager : MonoBehaviour
{
    List<DataModelPOI> dataCollectionPOI = new List<DataModelPOI>();

    void Start()
    {
        ReadFile();

        SpawnPOI();
    }

    void Update()
    {
        int count = dataCollectionPOI.Count;
        for (int i = 0; i < count; i++)
        {
            UpdatePOIPosition();
        }
    }

    void ReadFile()
    {
        TakeDataFromFile();
        for (int i = 0; i < ength; i++)
        {
            DataModelPOI dataPOI = new DataModelPOI(m_namePoi[i], m_namePoi[i], _locations[i]);
            dataCollectionPOI.Add(dataPOI);
        }
    }

    private void SpawnPOI()
    {
        for (int i = 0; i < dataCollectionPOI.Count; i++)
        {
            DataModelPOI dataPOI = dataCollectionPOI[i];
            var instance = Instantiate(m_POIPrefab);
            instance.name = "POI_" + m_namePoi[i];
            dataPOI.m_gameObject_POI = instance;
            dataPOI.m_gameObjectTooltip = m_panelTooltipPOI;
            dataPOI.m_gameObjectPanel = m_panelPOI;
        }
    }

Now I need to register Event associate to GameObject instantiate before. I want to do that in my EventManager. How can I point to dataCollectionPOI in EventManager class created and feeded in DataManager? Thanks for your time.

Behnam Sattar Behnam Sattar · Accepted Answer · 2019-04-17T01:37:41

Based on my understanding your question is mostly a design question. In first part of this answer, I'm giving you a suggestion for doing the design and keeping a reference to your objects. In second part I'll give you some tips regarding performance.

[I'm using RootObject instead of Object to refer you the main GameObject you create.]

Design

Let's break down our needs and then come up with a solution for each.

First we want to read some text file and then get some data from that. This data will be used later for creation of GameObjects. For now let's just focus on the data itself.

What we want here is a manager class which reads the file for us and stores the data in some form. We access this manager later and ask for our data in order to create the GameObjects.

This manager class stores our data in a collection of data objects [notice here we're talking about plain objects and not Unity's GameObjects]. You need to design this data class based on each line of text you have. Optionally, you can also keep the references to GameObjects here too.

Assume you're reading three string values from each line, named ValueOne, ValueTwo, and ValueThree, and you want to keep reference to three GameObjects called RootObject, ToolTip and Panel. For such purpose you can define following class:

public class DataModel {

  // Values read from text file.
  public string valueOne { get; private set; }
  public string valueTwo { get; private set; }
  public string valueThree { get; private set; }

  // Placeholders for GameObjecs created at runtime.
  public GameObject rootObject;
  public GameObject tooltipObject;
  public GameObject panelObject;

  public DataModel(string valueOne, string valueTwo, string valueThree){
    this.valueOne = valueOne;
    this.valueTwo = valueTwo;
    this.valueThree = valueThree;
  }
}

Then in your manager class you can create a collection (a List for example) for holding your data. Your manager class should read the text file at some point and populate this list with instances of DataModel. It will be something like this:

public class DataManager {

  List<DataModel> dataCollection = new List<DataModel>();

  public void ReadFile() {

    // Here you need to read the file and get the values you need.
    // The actual code should be different from what I'm putting here.

    foreach(string line in lines) {
      // You get valueOne, valueTwo and valueThree
      // from each line and maybe prepare them 
      // (maybe you need conversion from string to int)

      DataModel data = new DataModel(valueOne, valueTwo, valueThree);
      dataCollection.Add(data);
    }
  }
}

After you call the method on manager to read the data, you'll have your data prepared for you whenever you want to use it.

It's time to create objects based on the data and save the reference.

for (int i = 0; i++; i <= manager.dataCollection.Count) {
  DataModel data = manager.dataCollection[i];
  data.rootObject = instantiate() // You instantiate the root GameObject here.
  data.tooltip = instantiate() // You instantiate the tooltop GameObject here.
  data.panel = instantiate() // You instantiate the panel GameObject here.
}

Done. Now you have a manager class which has reference to all the data and also GameObjects which are created based on this data.

Performance

It might not be a good idea to do this all in runtime as it might cause frame drops in your game. If this is a problem you can try object pooling. If you search for that you should be able to find great tutorials on how to perform object pooling.

If you ended up not using object pooling, you can still remedy any performance drops by instantiating only one GameObject per frame. This can be done using Coroutines. You just need to do a yield return new WaitForEndOfFrame() in your loop of instantiation.

Final Note

Keep in mind that this all a suggestion and I don't think there is one single best answer to your question. Make sure you try to understand what tools are at your disposal and try them all before deciding on one solution. :)

How to maintain reference to object instantiate at runtime in Unity

3 Answers