“生成”游戏对象的正确方法。 （我想生成射弹）

Question

Hey all I made the following class to act as "bullets" in my game and I don't know how to construct these bullet objects with the params that I want (determined at runtime) and spawn them in the game.

My first attempt looked like this:

 if (canShoot())
        {
            shotCoolDown = FRAMES_BETWEEN_SHOTS;
            Bullet bullet = new Bullet().setLoft(LOFT).setWobble(WOBBLE).setInitialVel(INITIAL_VEL).setDirectionOffset(internalRecoil.getRecoil());
        }

but i get the following warnign from the unity editor:

You are trying to create a MonoBehaviour using the 'new' keyword. This is not allowed. MonoBehaviours can only be added using AddComponent(). Alternatively, your script can inherit from ScriptableObject or no base class at all

What is the proper way to spawn these bullets and to set the fields as I want them?

For more info here is the bullet class

 public class Bullet : MonoBehaviour
{
    private Rigidbody rigidbody;
    private float wobble;
    private float loft;
    private float initialVel;
    private Vector2 initialDirectionOffset;
    private bool wobbleDirection = false;
    
    private void Awake()
    {
        this.rigidbody = this.GetComponent<Rigidbody>();
    }

    private void Start()
    { 
        transform.Rotate(initialDirectionOffset); 
        rigidbody.AddForce(initialVel*transform.forward);
        rigidbody.AddForce(loft*transform.up);
    }

    private void FixedUpdate()
    {
        if (wobbleDirection)
        {
            rigidbody.AddForce(transform.right * wobble);
            wobbleDirection = false;
        }
        else
        {
            rigidbody.AddForce(-transform.right * wobble);
            wobbleDirection = true;
        }
    }

    public Bullet setWobble(float wobble)
    {
        this.wobble = wobble;
        return this;
    }
    
    public Bullet setLoft(float loft)
    {
        this.loft = loft;
        return this;
    }
    
    public Bullet setInitialVel(float initialVel)
    {
        this.initialVel = initialVel;
        return this;
    }

    public Bullet setDirectionOffset(Vector2 offset)
    {
        this.initialDirectionOffset = offset;
        return this;
    }
}

For more info here is the full "gun" class that spawns the bullets.

public class Gun : MonoBehaviour
{
    private int FRAMES_BETWEEN_SHOTS = 10;
    private int shotCoolDown = 0;
    private const float LOFT = 100F;
    private const float WOBBLE = 100F;
    private const float INITIAL_VEL = 100F;
    private Vector3 directionOffset;
    private Recoil internalRecoil;
    

    private void Awake()
    {
        internalRecoil = this.GetComponent<Recoil>();
        if (internalRecoil == null)
        {
            throw new Exception("Could not find recoil component");
        }
    }

    private void FixedUpdate()
    {
        if (shotCoolDown > 0)
        {
            shotCoolDown--;
        }
    }

    private bool canShoot()
    {
        return shotCoolDown == 0;
    }

    public void performShoot()
    {
        if (canShoot())
        {
            //need to have a recoil component that reacts to bullet fire. then adjusts back to 0,0,0
            shotCoolDown = FRAMES_BETWEEN_SHOTS;
            Bullet bullet = new Bullet().setLoft(LOFT).setWobble(WOBBLE).setInitialVel(INITIAL_VEL).setDirectionOffset(internalRecoil.getRecoil());
        }
    }
}

My second attempt looks like:

 GameObject.Instantiate(new Bullet().setLoft(LOFT).setWobble(WOBBLE).setInitialVel(INITIAL_VEL)
                .setDirectionOffset(internalRecoil.getRecoil()));

is this the right way to do it???

Answer 1

As 3Dave mentioned, the best way to do this would be to instantiate a prefab. Assuming you will be dealing with multiple projectiles, I like to separate this into a utility function for instantiating prefabs at a given position.

public static class UnityUtil {

    public static GameObject instantiatePrefab(
        Object prefab, 
        Vector3 position,
        Transform? parent = null
    ){
        // Create an instance of the prefab
        GameObject instance = Object.Instantiate(prefab, position, Quaternion.identity) as GameObject;

        // Set the parent
       if(parent != null){
          instance.transform.parent = parent;
       }

       return instance;
    }

}

Then you could have code like

Transform projectileHolder;
GameObject myBulletPrefab;
Vector3 bulletPosition;

...setup variables...


var BulletGameObj = UnityUtil.instantiatePrefab(myBulletPrefab, bulletPosition, projectileHolder);
Bullet bullet = BulletGameObj.GetComponent<Bullet>();

I keep some other functions in my util for dealing with generic gameobject cases, you can see my full UnityUtil class here