unity 按下鼠标左键随机生成物体Instantiate

using UnityEngine;
using System.Collections;

public class CreateObj : MonoBehaviour {
    public GameObject car;
    public float produceRate = 0.5f;
    private float nextProduce = 0;
    // Update is called once per frame
    void Update()
    {
        //Fire1默认对应摇杆的0号按键(鼠标左键)
        if (Input.GetButton("Fire1") && Time.time > nextProduce)
        {
            nextProduce = Time.time + produceRate;
            //当按下Fire1键时，每0.5秒生成一个汽车.
            Vector3 position = new Vector3(Random.Range(-5, 5), 1, Random.Range(-5, 5));
            GameObject clone = Instantiate(car, position, car.transform.rotation) as GameObject;
        }
    }

}