[Experimental] Smarter Predicate Buckets

hmans commented 2 years ago

This changes predicate buckets to re-evaluate their source's entities against the predicate every time the predicate bucket is iterated over, or the update() function is called.

it("automatically sees updated entities, like magic", () => {
  const bucket = new EntityBucket<Entity>()
  const john = bucket.add({ name: "John", age: 30 })
  const jane = bucket.add({ name: "Jane" })

  const old = bucket.archetype((entity) => Number(entity.age) > 25)
  expect([...old]).toEqual([john])

  john.age = 25
  expect([...old]).toEqual([])

  john.age = 30
  expect([...old]).toEqual([john])
})

Notes:

Explicitly calling archetype.update() is a potential solution for (part of) #154, as it would give more control to the user over when entities are added to or removed from the archetype.
We certainly don't want the same archetype to update itself 10 times per tick if it is iterated over 10 times (eg. by different systems.) This is a big big footgun that might mean this mechanism should maybe be disabled by default (requiring the user to explicitly invoke archetype.update() at an opportune time?)
There might be an opportunity to make ArchetypeBucket have a similar kind of auto-magic. Will need to ponder this further.

Todo:

[ ] Add a toggle that allows this automatic reindexing to be disabled. (If the values never change during the lifetime of entities, there is no need to reevaluate them on every iteration.)
[ ] Sleep on it 🛌

codesandbox[bot] commented 2 years ago

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hmans / miniplex