Adding Elements To An Array Using Array.Add

Question

I am new to C# and am trying to make a basic game in Unity. I am trying to add bullet gameObject to an array. I have researched how to add elements to an array in C# and have found the Add method. However, when I try to use this MonoDevelop doesn't highlight the method as if the method doesn't exist and I get an error. Here is is the error message:

Assets/Scripts/SpaceShipController.cs(126,25): error CS0118: SpaceShipController.gameManager' is afield' but a `type' was expected

Here is the line of code which trips the error:

gameManager.bullets[].Add(bulletObject);

Here is the rest of my code. The class called SpaceShipController trips the error when it tries to add bullet objects to an array in a GameManager objects with the script GameManager attached. Finally the BulletBehaviour class just makes the bullet move forward. The code is labelled by class:

SpaceShipController:

using UnityEngine;
using System.Collections;

public class SpaceShipController : MonoBehaviour {

    public GameObject bulletObject;

    public GameManager gameManager;

    //private GameObject[] bullets;

    public float shipSpeed;
    public float bulletSpeed = 1;

    private Vector3 spaceShip;

    private Quaternion spaceShipRotation;

    private Vector3 bulletPosition;

    private int coolDown = 10;

    private bool moveRight = false;
    private bool moveLeft = false;
    private bool fire = false;

    // Use this for initialization
    void Start () {

        spaceShip = transform.position;

        spaceShipRotation = transform.rotation;

        bulletObject.transform.position = bulletPosition;
    }

    // Update is called once per frame
    void Update () {

        coolDown--;

        inputHandler();

        this.transform.position = spaceShip;
    }

    void inputHandler() {

        if (Input.GetKeyDown(KeyCode.RightArrow)) {

            moveRight = true;

        }

        if (Input.GetKeyDown(KeyCode.LeftArrow)) {

            moveLeft = true;

        }

        if (Input.GetKeyUp(KeyCode.RightArrow)) {

            moveRight = false;

        }

        if (Input.GetKeyUp(KeyCode.LeftArrow)) {

            moveLeft = false;

        }

        if (Input.GetKeyDown(KeyCode.Space)) {

            fire = true;
        }

        if (Input.GetKeyUp(KeyCode.Space)) {

            fire = false;
        }

        if (moveRight == true) {

            spaceShip.x += shipSpeed;

        }

        if (moveLeft == true) {

            spaceShip.x -= shipSpeed;

        }


        if (coolDown <= 0) {

            if (fire == true) {

                Fire ();

                coolDown = 10;
            }

        }
    }

    void Fire () {

        for (var i = 0; i < 2; i++) {

            if (i == 0) {

                spaceShip = new Vector3 (transform.position.x + 0.9f, transform.position.y + 0.9f, transform.position.z);
            }

            else if (i == 1) {

                spaceShip = new Vector3 (transform.position.x - 0.9f, transform.position.y + 0.9f, transform.position.z);
            }

            Instantiate(bulletObject, spaceShip, spaceShipRotation);

            bulletObject.AddComponent<BulletBehaviour>();

            gameManager.bullets[].Add(bulletObject);

            spaceShip = this.transform.position;
        }
    }
}

GameManager:

using UnityEngine;
using System.Collections;

public class GameManager : MonoBehaviour {

    public GameObject[] bullets;

    public Camera cam;

    private Vector2 cameraBounds;

    // Use this for initialization
    void Start () {


        cameraBounds = new Vector2 (cam.orthographicSize * Screen.width/Screen.height, cam.orthographicSize);
    }

    // Update is called once per frame
    void Update () {

        /*for (int i = 0; i < bullets.Length; i++) {

            if (bullets[i].transform.position.y >= cameraBounds.y) {

                Destroy(bullets[i]);

            }
        }*/
    }
}

BulletBehaviour:

using UnityEngine;
using System.Collections;

public class BulletBehaviour : MonoBehaviour {

    public SpaceShipController ship;

    private Vector3 shipPosition;

    // Use this for initialization
    void Start () {

        shipPosition = transform.position;
    }

    // Update is called once per frame
    void Update () {

        shipPosition.y += 1;

        transform.position = shipPosition;
    }
}

As always any help would be greatly appreciated. Thanks in advance for any help you can provide.

When accessing the bullets variable, there is no need to have the [] brackets. You can say gameManager.bullets.Add(bulletObject); — Simon
– Simon, Commented Jul 12, 2014 at 16:42
@Simon That's right, the [] not needed to call methods on an array. But the bigger issue is, arrays have no Add method. — dcastro
– dcastro, Commented Jul 12, 2014 at 16:54
Also, for future reference, please provide the shortest code possible to recreate the issue, instead of a wall of text. The question is about how to add items to an array - you don't need to tell us about unity, and all those classes. See the Help Centre: How to create a Minimal, Complete, and Verifiable example — dcastro
– dcastro, Commented Jul 12, 2014 at 16:56

dcastro · Accepted Answer · 2014-07-12 16:47:26Z

3

Arrays are fixed-size. This means that, once they have been initialized with a certain length (e.g., bullets = new GameObject[10]), its length can no longer change.

In order to "add" an item to a array, you have to specify in which position you'd like the item to be. By default, arrays' indexing is 0-based. For example, to insert an element in the first position:

bullets[0] = myItem;

If you don't know how many items you'll have beforehand, and want to add/remove items at will, you should use a resizable collection, such as List<T>.

public List<GameObject> Bullets {get; set;}

You can use it like so:

//initialize with 0 items
Bullets = new List<GameObject>();

//add a new item at the end of the list
Bullets.Add(item);

3 Comments

msmolcic Over a year ago

Was about to post pretty much the same answer, but you beat me to it.. +1 :)

user3150583 Over a year ago

Thanks for the help, your suggestion worked well. How would you go about cycling through a List?

dcastro Over a year ago

@user3150583 You can cycle through a list's items using a foreach construct. If you scroll to the bottom of the documentation page for List<T> (linked on my answer), you'll see a few useful examples on how to use a list. The MSDN documentation is a great place to start learning C#.

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