Components

A component is data associated with an entity, differentiated by its schema, a uniquely identifiable template. Or, more specifically, that schema's integer id.

Schema

A schema is defined using Harmony's createSchema function:

const Health = createSchema(formats.float64)

Harmony exports a formats object which contains multiple numeric types, e.g. uint8, int16, float64, etc.

Native Components

The term "native" here is misleading; as we will see, the other kind of component that Harmony can store is powered by a native, although esoteric, language feature.

Native components store plain built-in JavaScript values. This currently includes numbers and objects, and will include arrays, maps, and sets in the near future.

We have already defined a number component in the Health component example above. Any of Harmony's numeric formats (uint, int, float) do not matter here: the component is simply stored in an array of built-in, IEEE 754 numbers.

Native object components are created by providing an object to makeSchema, where each key is a fixed property name, and its value is either a format or a nested object conforming to the same rules:

const Attributes = createSchema({
  strength: formats.uint8,
  dexterity: formats.uint8,
  // ...
  modifiers: {
    strength: formats.int8,
    // ...
  },
})

A component can be added to or removed from an entity using set and unset, respectively. Components are then modified using queries.

Binary Components