如何向现有编队添加/销毁新对象？

Question

In the manager:

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class FormationsManager : MonoBehaviour
{
    public Transform squadMemeberPrefab;
    public int numberOfSquadMembers = 20;
    public int columns = 4;
    public int gaps = 10;
    public Formations formations;

    private int numofmembers;

    // Use this for initialization
    void Start()
    {
        numofmembers = numberOfSquadMembers;
        formations.Init(numberOfSquadMembers, columns, gaps);
        GenerateSquad();
    }

    // Update is called once per frame
    void Update()
    {
        if (numofmembers != numberOfSquadMembers)
        {
            GenerateSquad();
        }
    }

    private void GenerateSquad()
    {
        Transform go = squadMemeberPrefab;

        for (int i = 0; i < formations.newpositions.Count; i++)
        {
            go = Instantiate(squadMemeberPrefab);
            go.position = formations.newpositions[i];
            go.tag = "Squad Member";
            go.transform.parent = gameObject.transform;
        }
    }
}

And the Formations script:

using System;
using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class Formations : MonoBehaviour
{
    public List<Vector3> newpositions;

    private int numberOfSquadMembers;
    private int columns;
    private int gaps;
    private List<Quaternion> quaternions;

    private Vector3 FormationSquarePositionCalculation(int index)
    {
        float posX = (index % columns) * gaps;
        float posY = (index / columns) * gaps;
        return new Vector3(posX, posY);
    }

    private void FormationSquare()
    {
        newpositions = new List<Vector3>();
        quaternions = new List<Quaternion>();

        for (int i = 0; i < numberOfSquadMembers; i++)
        { 
            Vector3 pos = FormationSquarePositionCalculation(i);
            Vector3 position = new Vector3(transform.position.x + pos.x, 0, transform.position.y + pos.y);
            newpositions.Add(position);
        }
    }

    public void Init(int numberOfSquadMembers, int columns, int gaps)
    {
        this.numberOfSquadMembers = numberOfSquadMembers;
        this.columns = columns;
        this.gaps = gaps;
        FormationSquare();
    }
}

What I want to do is in the FormationsManager in the Update not only just calling GenerateSquad but to add the new once to the last/next position of the existing already formation.

void Update()
        {
            if (numofmembers != numberOfSquadMembers)
            {
                GenerateSquad();
            }
        }

If the value of numberOfSquadMembers is 20 first time and then I changed it to 21 add new object to the end of the formation and same if I change the value of numberOfSquadMembers for example from 20 to 19 or from 21 to 5 destroy the amount of objects from the end and keep the formation shape.

The soldiers the last line is on the right side. So if I change the value to add more then add it to the right and if I change to less destroy from the right side. The most left line of soldiers is the first.

Answer 1

It is possible if you keep GameObject instances inside FormationsManager class, and then reuse them in GenerateSquad method.

In FormationsManager class, add and modify code as follows.

public GameObject squadMemeberPrefab;
List<GameObject> SquadMembers = new List<GameObject>();

void Update()
{
    if (numofmembers != numberOfSquadMembers)
    {
        numofmembers = numberOfSquadMembers;
        formations.Init(numberOfSquadMembers, columns, gaps);
        GenerateSquad();
    }
}

private void GenerateSquad()
{
    Transform go = squadMemeberPrefab;
    List<GameObject> newSquadMembers = new List<GameObject>();

    int i = 0;
    for (; i < formations.newpositions.Count; i++)
    {
        if (i < SquadMembers.Count)
            go = SquadMembers[i];
        else
        {
            go = Instantiate(squadMemeberPrefab);
            newSquadMembers.Add(go);
        }
        go.position = formations.newpositions[i];
        go.tag = "Squad Member";
        go.transform.parent = gameObject.transform;
    }

    for (; i < SquadMembers.Count; i++)
        Destroy(SquadMembers[i]);

    SquadMembers = newSquadMembers;
}

However, I recommend you to consider GameObject Pool (Object Pool), which can thoroughly resolve such object recycle problem. For this purpose, you can use ClientScene.RegisterSpawnHandler. Go to this Unity Documentation page and search text "GameObject pool". You can see an example code there.