System:add_query

Instantiates a new Query.

This function can only be called before spawning any entity. It will error when called while any entity exists.

Usage

system:add_query(classes)

Arguments

Name	Type	Description
classes	table	List of component classes this query uses to filter entities.

Each entry in the classes table can be either a component subclass, or its name as a string.

Returns

Name	Type	Description
query	Query	Query that was created by this call.

Examples

local Health = Class("Health", crystal.Component);
local Poison = Class("Poison", crystal.Component);
local PoisonSystem = Class("MySystem", crystal.System);

PoisonSystem.init = function(self)
  self.query = self:add_query({ "Health", Poison });
end