User Data for Entities

It is often useful to differentiate entities from each other. For example scripting a behavior, based on the entity we touch (e.g. from physics). When working engine-only, its not much of an issue, as we can just modify the entity on instantiation, giving it extra properties needed. This feature is probably more beneficial for Editor projects.

At the moment, there are mainly two ways to differentiate entities under the same parent:

• by tag
• by name

Tags are pretty powerful, and allow filtering assets and entities, among other cookies. However, the tags are better suited for use during load times, rather than to be used during mid-life of the app:

// we have to first search the tag (e.g. we try to store a number in it)
if (entity.tags.has('intensity')) {
    // then convert string to number
    const str = entity.tags.list[0];
    const intensity = parseInt(str);
    // use intensity number
}

It would be much more efficient to allow to store a user defined number directly on the entity. Similar to how physics engines allow to store a user defined number for association, the entities could have a userData field for storing a plain number.

const intensity = entity.userData;

No file, test, or entry point is named. Start by locating the entity implementation and the existing tag and name APIs, then determine where a userData value belongs in the entity lifecycle. Done means an entity can store and retrieve a user-defined number through entity.userData, with behavior covered by an appropriate test.