System

Systems in Ecstatic are just functions that are associated with a group of Components. Whenever the systems are "run", the function is called on every Entity that has all the Components associated with that System.

Defining a system#

Systems are added to the World instance with the world.addSystem() method.

Systems are "run" with the world.systems.run() method.

The order that systems are added specifies the order in which they are run.

const setTransformComps = [Position, Rotation, Scale, GameBody];

const setTransform = (args) => {
  // do system-y stuff;
  const { components } = args;
  const position = components.get(Position);
  const rotation = components.get(Rotation);
  const scale = components.get(Scale);
  const gamebody = components.get(GameBody);

  gamebody.setTransform(position, rotation, scale);
};

world.addSystem(setTransformComps, settransform);

// elsewhere, probably in a render loop.
world.systems.run();

System function arguments#

const mySystem = (args) => {
  const {
    /**
     * The current entity being iterated.
     */
    entity,
    /**
     * The components that belong to the entity
     */
    components,
    /**
     * The World instance.
     * Use this to access other entities.
     */
    world,

    /**
     * The index of the current entity in all entities to be run on this system.
     */
    index,
    /**
     * This size of all the entities will run on this system.
     */
    size,
    /**
     * Is the first entity to be iterated on this run of a system.
     * Helpful for setting up state that is the same for all entities only once.
     */
    isFirst,
    /**
     * Is the last entity to be iterated on this run of a system.
     * Can be helpful to tear down anything that should be dealt with after all the entites have ran.
     */
    isLast,
  } = args;
}