Guide to Building ViewBindings

You can also build your own ViewBindings.

ViewBindings connect data in the DataStore to UI. There are a set of basic ViewBindings that are provided with GPF. The basic ViewBindings are very useful, however sometimes you will need UI for a data structure that there isn't an existing ViewBinding for, and it's in those instances where you will want to create your own.

This guide walks you through LeaderboardVB, a custom ViewBinding included with the Single-Player / Leaderboard Demo. On first glance, it might not seem nessary to create a new ViewBinding since a leaderboard is just an a list of objects, and ListVB can already handle that. However, we chose to use an unorthadox data structure for the leaderboard, specifically

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Tuple<string, int>[]

thus, we need to write a new ViewBinding that assumes variable is of this type.

Let's zoom in to perhaps the least obvious line of code in LeaderBoardVB.cs. The last line of the Start() function reads:

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props.AddListener<Tuple<string, int>[]>(variable, Listener);

Here, props gives us the ability to listen to the DataStore for changes to variable, and run Listener when those changes occur. Infact Listener will also be run as soon as the listener is added to props. The necisity for each ViewBinding to use props to gain access to the DataStore motivates the preceding line as well:

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Props.Inject(this);

The code above causes props to be able to access the DataStore and forces our LeaderboardVB class to implement IPropReceiver.

The rest of the code is straight forward as the Listener function simply leverages it's intimate knowledge of the data structure used by variables as well as it's intimate knowledge of the UI in play ,spots, to set the UI approprietely.

Here is the complete LeaderboardVB class with comments:

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public class LeaderboardVB : MonoBehaviour, IPropReceiver
{
    // Props give this ViewBinding a unique view of data from the DataStore
    public Props props { get; set; }
    // A DataPath field enables autocomplete in the Unity Editor
    public DataPath variable;
    // The places on the leader board we want to display
    [Serializable]
    public class Spot
    {
        public Text username;
        public Text score;
    }
    public Spot[] spots = new Spot[0];
    void Start()
    {
        // Get our props. Props can be provided from parent objects in the hierarchy
        Props.Inject(this);
        // We want the UI to be updated every time the data changes
        // The change listener will be called whenever the variable value changes
        props.AddListener<Tuple<string, int>[]>(variable, Listener);
    }
    void Listener(Tuple<string, int>[] scores)
    {
        for (int i = 0; i < spots.Length; i++)
        {
            if (scores.Length > i)
            {
                spots[i].username.text = scores[i].Item1;
                spots[i].score.text = scores[i].Item2.ToString();
            }
            else
            {
                spots[i].username.text = "";
                spots[i].score.text = "";
            }
        }
    }
}