Sharing data in a list between two classes

Question

I'm trying to make a camera in Unity through an external settings file. At the moment I have that file being read in and its values stored as follows:

    public struct Entry
{
    public System.Object value;
    public Type type;
}

public class HV_ReadSettingsFile : MonoBehaviour

{
    Entry _screenEntry;
    Entry _cameraEntry;


public Dictionary<string, Entry> cameraDictionary = new Dictionary<string, Entry>();
public List<HV_Camera> cameraList = new List<HV_Camera>();
public List<HV_Screen> screenList = new List<HV_Screen>();




// Use this for initialization
void Start()
{
    StoreXMLValues();

}

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

void StoreXMLValues()
{
    var xdoc = XDocument.Load(@"C:\\Test.xml");
    var screens = xdoc.Descendants("Screen");
    var cameras = xdoc.Descendants("Camera");


    foreach (var screen in screens)
    {
        HV_Screen _screen = new HV_Screen();
        _screen.Name = (string)screen.Element("Name").Attribute("Name");
        _screen.Tag = (string)screen.Element("ScreenTag").Attribute("Tag");
        _screen.XPOS = (string)screen.Element("LocalPosition").Attribute("X");
        _screen.YPOS = (string)screen.Element("LocalPosition").Attribute("Y");
        _screen.ZPOS = (string)screen.Element("LocalPosition").Attribute("Z");
        _screen.Width = (string)screen.Element("Width").Attribute("Width");
        _screen.Height = (string)screen.Element("Height").Attribute("Height");
        _screen.YAW = (string)screen.Element("Orientation").Attribute("YAW");
        _screen.PITCH = (string)screen.Element("Orientation").Attribute("PITCH");
        _screen.ROLL = (string)screen.Element("Orientation").Attribute("ROLL");



        //Debug.Log("Screen name: " + _screen.Name);
        //Debug.Log("Screen tag: " + _screen.Tag);
        //Debug.Log("Screen xpos: " + _screen.XPOS);
        //Debug.Log("Screen ypos: " + _screen.YPOS);
        //Debug.Log("Screen zpos: " + _screen.ZPOS);
        //Debug.Log("Screen width: " + _screen.Width);
        //Debug.Log("Screen height: " + _screen.Height);
        //Debug.Log("Screen Yaw: " + _screen.YAW);
        //Debug.Log("Screen Pitch: " + _screen.PITCH);
        //Debug.Log("Screen Roll: " + _screen.ROLL);
        screenList.Add(_screen);
    }

    foreach (var camera in cameras)
    {
        HV_Camera _camera = new HV_Camera();
        _camera.Name = (string)camera.Element("Name").Attribute("Name");
        _camera.Tag = (string)camera.Element("CameraTag").Attribute("Tag");
        _camera.XPOS = (string)camera.Element("LocalPosition").Attribute("X");
        _camera.YPOS = (string)camera.Element("LocalPosition").Attribute("Y");
        _camera.ZPOS = (string)camera.Element("LocalPosition").Attribute("Z");
        _camera.YAW = (string)camera.Element("Orientation").Attribute("Yaw");
        _camera.PITCH = (string)camera.Element("Orientation").Attribute("Pitch");
        _camera.ROLL = (string)camera.Element("Orientation").Attribute("Roll");
        _camera.Near = (string)camera.Element("Near").Attribute("Near");
        _camera.Far = (string)camera.Element("Far").Attribute("Far");
        _camera.FOV = (string)camera.Element("FOV").Attribute("FOV");
        _camera.AspectRatio = (string)camera.Element("AspectRatio").Attribute("AspectRatio");
        _camera.ScreenDistance = (string)camera.Element("ScreenDistance").Attribute("ScreenDistance");

       // Debug.Log("Camera name: " + _camera.Name);
        cameraList.Add(_camera);

    }

    //Debug.Log("Camera Count: " + cameraList.Count);

    //Debug.Log("Screen Count: " + screenList.Count);
}

public List<HV_Camera> GetCameraList()
{
   // Debug.Log("Got list");
    return cameraList;
}

I've tested this with the commented out Debug.Logs and I know that my settings file is getting read in and the values stored.

In my HV_Camera class, I'm trying to access the data in the cameraList. This is what I have:

     HV_ReadSettingsFile settings;
        List<HV_Camera> testCamera = new List<HV_Camera>();

void Start () 
{
   settings = gameObject.GetComponent<HV_ReadSettingsFile>();
 GetList();
   CreateCamera();
}

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

}


public void GetList()
{
    testCamera = settings.GetCameraList();


}

public void CreateCamera()
{

    for (int i = 0; i < testCamera.Count; i++)
    {
        Debug.Log("I am camera");
    }


}

Now, in that for loop, I'm simple wanting to see if the data is getting passed over. If it works, "I am a camera" should get printed out 4 times. But this isn't the case. Is there something I'm missing or not doing correctly?

Answer 1

I suspect the problem is in the order of script execution. All of your logic is in the Start methods of the components, and you've no guarantee that HV_ReadSettingsFile.Start() will run before HV_Camera.Start() .

Most likely HV_Camera is running first, before your settings list is populated. It's possible to set a priority order for scripts in the Unity IDE to ensure that this doesn't happen, though I find this a little unintuitive from a developer perspective.

Alternatively, you can restructure your code to ensure that the code is run in the correct order. For example, if you made a public method HV_ReadSettingsFile.EnsureFileIsRead() , you can call that method from the Start() of both components. The method should use a flag to record whether it's already been run, and thus ensure that the code is run exactly once, and for whichever component requires it.