同一对象在C＃中一次又一次地实例化

Question

我是编码的初学者。 我一直在尝试重新创建流行的手机游戏“ Crossy Road”。 当我尝试创建一个关卡生成脚本时，遇到了一个问题。 我面临的问题是，当我尝试随机实例化3个不同的对象（在本例中为“草”，“路”和“水”）时，只会生成草。 如果有人能告诉我为什么它不断重复实例化“ Grass”对象，我将不胜感激。 我正在Unity 5 Fyi中重新创建游戏。 代码如下-

using UnityEngine;
using System.Collections;

public class LevelGenerationScript : MonoBehaviour {

public GameObject Water;
public GameObject Road;
public GameObject Grass;
int firstRand;
int secondRand;
int distPlayer = 10;

Vector3 intPos = new Vector3(0,0,0);

void Update () 
{
    if (Input.GetButtonDown("up")) 
    {
        firstRand = Random.Range(1,4);
        if(firstRand == 1)
        {
            secondRand = Random.Range(1,8);
            for(int i = 0;i < secondRand; i++)
            {
                intPos = new Vector3(0,0,distPlayer);
                distPlayer += 1;
                GameObject GrassIns = Instantiate(Grass) as GameObject;
                GrassIns.transform.position = intPos;
            }

            if(firstRand == 2)
            {
                secondRand = Random.Range(1,8);
                for(int i = 0;i < secondRand; i++)
                {
                    intPos = new Vector3(0,0,distPlayer);
                    distPlayer += 1;
                    GameObject RoadIns = Instantiate(Road) as GameObject;
                    RoadIns.transform.position = intPos;
                }

                if(firstRand == 3)
                {
                    secondRand = Random.Range(1,8);
                    for(int i = 0;i < secondRand; i++)
                    {
                        intPos = new Vector3(0,0,distPlayer);
                        distPlayer += 1;
                        GameObject WaterIns = Instantiate(Water) as GameObject;
                        WaterIns.transform.position = intPos;
                    }
                }
            }
        }
    }
}
}

如果有人可以告诉我这个错误，我将非常感激。 谢谢！

Answer 1

您已将其他对象的代码放置在firstRand为1时调用的代码组内。（FirstRand == 2）和（FirstRand == 3）在此位置永远都不是，您编写了无法访问的代码。

Answer 2

您的if (firstRand == 2)语句将永远不会到达，因为它包含在if (firstRand ==1)语句中。

您需要像下面这样构造if语句：

if (firstRand == 1)
{
   ...
}

if (firstRand == 2)
{
   ...
}

if (firstRand == 3)
{
   ...
}

如果您想改进代码，则应执行以下操作：

firstRand = Random.Range(1,4);
secondRand = Random.Range(1,8);
GameObject instance = null;

for (int i = 0; i < secondRand; i++)
{
    intPos = new Vector3(0, 0, distPlayer);
    distPlayer += 1;

    switch (firstRand)
    {
        case 1:
            instance = Instantiate(Grass) as GameObject;
            break;
        case 2:
            instance = Instantiate(Road) as GameObject;
            break;
        case 3:
            instance = Instantiate(Water) as GameObject;
            break;
    }

    instance.transform.position = intPos;
}