World:query method to filter when needed

[pablomayobre]

This proposal is for a method that allows you to query the World for all entities that match a Filter, and perform an action on them, including modifying/adding/removing Components or even destroying the Entity.

World:query({"position", "ai", "!boss"}, function (entity)
  entity:give("something")
end)

The function (callable) could be optional and when not specified, it could return an array containing the Entities, or alternatively if a table is passed instead of a function, it would be filled with said Entities.

WARNING

This method would be far more expensive than just using a Pool in a System, and its main usage would be for things that happen once, for example upgrading the components of deserialized Entities to newer versions, removing all entities that were destroyed in a frame, etc. All this actions may not need their own Pools, since the Entities affected by them are not used repeatedly.

Then again this is NOT a recommended function:

It's expensive

• It needs to loop through all the Entities and perform a Filter check.

Generates Garbage

• A Filter is built in the process.
• The required function will most likely be used once only.
• If a table is returned instead, that table will only be valid at the callsite of the function.