Derivable

Derivable is a type that combines a molecule:

type MoleculeThatReturnsAString = () -> string

and a constant:

type Constant = string

into one. This is what a Derivable looks like internally:

type Derivable<T> = T | () -> T

Usage

Say you have a table like so:

type Props = {
    count: Molecule<number>
}

local props: Props = { count = flec(0) }

print(peek(props.count))

And you want your peek to detect constants as well as state objects. You can do so by doing this:

type Props = {
    count: Derivable<number>
}

local props: Props = { count = flec(0) }

print(peek(props.count)) --> 0

By setting count's value type to Derivable<number>, we can do something like:

props.count = 0

print(peek(props.count)) --> 0

and the code will still work as expected. Pretty neat, huh?

Be mindful of Derivable angle brackets

Consider the following type definitions carefully:

Derivable<Vector3>?

This type definition means that it will only accept:

• Vector3

• A molecule that returns a Vector3 object

• nil (if the user doesn't specify a property value)

This type is best used for optional properties, where you provide a default value if not specified by the user.

Derivable<Vector3?>

This type definition means that it will only accept:

• Vector3, or nil

• A molecule that returns a Vector3 object, or nil

This type works best in situations where the property understands nil as a valid value. The user can set it to nil at any time.