Members and fields✎

A value often holds other values: a table of settings, an instance with properties. Two nodes read one out, and which you want depends on a single question — does anything know what is in there?

A type you declared

A type is declared by a Declare Type node — at the top of the file or where it sits — and what it is written as decides whether it has members to offer. A table of fixed fields does; everything else is a type Luau understands and this cannot enumerate.

The type's name is what travels. A Declare Local, a function's parameter, a variable or a Cast set to Input gives a pin typed Input, and every pin typed Input offers the same fields — the declaration is read wherever it sits in the file, including from inside a function.

export type Input = {
	throttle: number,
	steer: number,
	aim: Vector3,
}

local input: Input = {
	throttle = 1,
	steer = 0,
	aim = Vector3.zAxis,
}
print(input.aim)

export type Shot = { damage: number, from: Vector3 }

local shot: Shot = { damage = 25, from = Vector3.zero }
print(shot.damage)

export type Scores = { [string]: number }

local scores: Scores = { alice = 12, bob = 9 }
print(scores.alice)

A type a module exports

A module's exported types are offered here too, under the name this graph writes them as: require Tank.Config as Config, and a value annotated Config.Tuning offers that type's fields. The fields are read from the graph that declares them, so renaming one there changes what is offered here.

local ReplicatedStorage = game:GetService("ReplicatedStorage")
local Config = require(ReplicatedStorage.Tank.Config)
local tuning: Config.Tuning = Config.tuning
print(tuning.turnRate)

Both nodes appear, and which is which is the point. The module's own table is a value nothing here can describe — Roswaal does not read the other file's returns — so Config.tuning is a Get Field. What comes out is annotated as a type that is described, so turnRate off it is a Get Member.

A Roblox instance

An instance's properties come from the engine, so they need no declaring. A node that names a class hands back that class — New Instance set to Part gives a Part — and a Part's properties are then what Get Member offers.

local part: Part = Instance.new("Part")
if part.Anchored then
end

Inherited properties are there too: Name and Parent come from Instance, and a Part offers them alongside its own. Get Service gives the service's own class, and the Find First Child and Ancestor nodes follow their Class Name, so each of those leads straight into a member without a cast first.

Finding one

When there is no list

A table whose keys come and go while the program runs has no fixed members, and nothing offers any: that is Get Field, which takes the key as a pin and reads whatever is there. A key that is not a Luau name — a number, or a string with a space in it — is Get Field's as well, since t.my key is not something Luau can write.

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