FAQ.md

FAQ

Is there a string type for components?

Strings are expensive and usually unnecessary to have the ECS handle. For enum type strings, it is advised to create a mapping of integer to string, and store the integer in the component data as a reference to a string. This makes string serialization minimal and fast.

Otherwise, you can define a preallocated ui8 array and encode strings into that with a TextEncoder.

const maxStringLength = 32
const SomeComponent = defineComponent({ string: [Types.ui8, maxStringLength] })
const encoder = new TextEncoder()
SomeComponent.string[eid].set(encoder.encode("hello, world!"))

How do I set an undefined value for a property of type eid?

The eid type is defined internally as an unsigned integer, so it cannot have an undefined or null value and setting it to a negative value will cause it to overflow to INT_MAX. Instead, create a "null entity" directly after world creation. This will reserve the eid of 0 that you can then use to represent an undefined eid property.

Can I set default values for my component's properties?

You cannot set default values via addComponent calls. You must either create functions that explicitly set default values after adding the component, or you can achieve deferred default values by utilizing enter queries:

const SomeComponent = defineComponent({ value: Types.f32 })
const someQuery = defineQuery([SomeComponent])
const enterSomeQuery = enterQuery(someQuery)

const setDefaultValuesForSomeComponent = eid => {
  SomeComponent.value[eid] = 1
}

enterSomeQuery.forEach(setDefaultValuesForSomeComponent)