如何使用 range 属性添加更多新的实例化对象或删除对象？

Question

using System;
using UnityEngine;
using Random = UnityEngine.Random;
using System.Collections;
using System.Collections.Generic;
using System.Linq;

[ExecuteAlways]

public class CloneObjects : MonoBehaviour
{
    public Terrain terrain;
    public GameObject prefab;
    public GameObject parent;
    [Range(10, 1000)]
    public int numberOfObjects;
    public float yOffset = 10f;

    private float terrainWidth;
    private float terrainLength;
    private float xTerrainPos;
    private float zTerrainPos;

    void Start()
    {
        //Get terrain size
        terrainWidth = terrain.terrainData.size.x;
        terrainLength = terrain.terrainData.size.z;

        //Get terrain position
        xTerrainPos = terrain.transform.position.x;
        zTerrainPos = terrain.transform.position.z;

        generateObjectOnTerrain();
    }

    void generateObjectOnTerrain()
    {
        for (int i = 0; i < numberOfObjects; i++)
        {
            //Generate random x,z,y position on the terrain
            float randX = UnityEngine.Random.Range(xTerrainPos, xTerrainPos + terrainWidth);
            float randZ = UnityEngine.Random.Range(zTerrainPos, zTerrainPos + terrainLength);
            float yVal = Terrain.activeTerrain.SampleHeight(new Vector3(randX, 0, randZ));

            //Apply Offset if needed
            yVal = yVal + yOffset;

            //Generate the Prefab on the generated position
            GameObject objInstance = Instantiate(prefab, new Vector3(randX, yVal, randZ), Quaternion.identity);
            objInstance.name = "Waypoint";
            objInstance.tag = "Waypoint";
            objInstance.transform.parent = parent.transform;
        }
    }
}

I want that if I move in the editor either in edit mode or run time mode the numberOfObjects range to the right add new instantiated objects for example if there is 100 objects and I moved the Range slider to the right to 300 then add more 200 new objects. And if I move the slider to the left for example there is 100 objects and I moved it to the left to 70 then remove 30 objects or if I first moved it to the right added 200 objects and now there are 300 and then moved it to the left to 221 the remove the need number of objects.

Answer 1

Instead of using [Execute always] and Update you should rather do your stuff in OnValidate

This function is called when the script is loaded or a value is changed in the Inspector (Called in the editor only).

Then you need something to keep track of already created objects. Since you make them all children of parent you can simply check its Transform.childCount

The number of children the parent Transform has.

So you could do eg

private void OnValidate()
{
    if(parent.transform.childCount > numberOfObjects)
    {
        if(Application.isPlaying)
        {
            // Since destroy is done delayed we have to use a fix loop
            for(var i = parent.transform.childCount; i > numberOfObjects; i--)
            {
                Destroy(parent.transform.GetChild(0).gameObject);
            }
        }
        else
        {
            // DestroyImmediate however is executed immediately so
            // here we can simply rely on the childCount directly
            while(parent.transform.childCount > numberOfObjects)
            {
                DestroyImmediate(parent.transform.GetChild(0).gameObject);
            }
        }
    }

    while(parent.transform.childCount < numberOfObjects)
    {
        //Generate random x,z,y position on the terrain
        var randX = UnityEngine.Random.Range(xTerrainPos, xTerrainPos + terrainWidth);
        var randZ = UnityEngine.Random.Range(zTerrainPos, zTerrainPos + terrainLength);
        var yVal = Terrain.activeTerrain.SampleHeight(new Vector3(randX, 0, randZ));

        //Apply Offset if needed
        yVal = yVal + yOffset;

        //Generate the Prefab on the generated position
        var objInstance = Instantiate(prefab, new Vector3(randX, yVal, randZ), Quaternion.identity);
        objInstance.name = "Waypoint";
        objInstance.tag = "Waypoint";
        objInstance.transform.parent = parent.transform;
    }
}

Answer 2

Half of a possible solution is already in your code. You are using the ExecuteAlways attribute, and you are instantiating your objects with a for loop. The next step is to put the returned intance of your object in an array. That way, the reference to your gameObjects will not be lost forever when the current iteration of the for loop ends.

objects[i] = Instantiate(/*...*/);
objects[i].name = "Waypoint";
/*...*/

Once you have your GameObject[] objects array of gameObjects you can update it in the Update() method of your class: disable all objects with an index greater than your numberOfObjects , enable the rest. Since Update() doesn't get called every frame when the game is not running but only when something in the scene changes, then you shouldn't have performance issues. But when you are in Play Mode then checking up to 1000 gameObjects every frame could take some time, so you want to keep that in mind. You could do like this:

private void Update() {
    if (!Application.isPlaying) {
        //Update array
    }
}

PS. When asking the next answer, include in your post an attempted solution that shows that you put effort into solving your problem