johan helsing.studio

UniRx observable reference

UniRx is a great reactive programming library for Unity. However, I found it a bit difficult to write a clean reusable and decoupled user interface, so I wrote a small add-on library for UniRX which I think solves the problem quite nicely.

So the problem I was trying to solve is pretty basic. I was writing a score counter and I wanted to write it in such a way that I could re-use it in another project without rewriting any way. In other words I wanted it to be independent of the data model.

Basically I was trying to turn this:

public class Player : MonoBehaviour
{
    public IObservable<int> ScoreAsObservable { get; set; }
    // ...
}

public class Score : MonoBehaviour
{
    [SerializeField] private Player player;
    void Start()
    {
        player.ScoreAsObservable.SubscribeToText(GetComponent<Text>());
    }
}

Into something where the score didn’t have to know the details about how the Player works.

What I came up with, was UniRx Obervable Reference. It basically works like this:

If you need to expose a plain setter on your UI component, i.e.

public class SetTextFromInt : MonoBehaviour
{
    [SerializeField] private Text text;
    public SetFromInt(int value) => text.text = value.ToString();
}

Now the rest is done with generic components through the Unity inspector :) First, add the component, Int Observable Listener

added the Int Obserable Listener

Then select the game object with the score on it, and a compatible property from the dropdown. You can select any property that is assignable to a IObservable<int>. I.e. it doesn’t matter if it’s a ReactiveProperty<int>, or a IObservable<int> or a IntReactiveProperty property.

select the game object and property

Then, just add a handler to set the value:

image-20200601153407575

And that’s it.

Now I can move the score component to another project, and all I have to do, is assign a new IObservable<int> property using the inspector.

It can be installed as a upm package. Here is the source: github.com/johanhelsing/unirxobservablereference

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