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Recap: Fine-Tuning Types

Part of the Introduction To Luau section of Coddy's Lua journey. Lesson 80 of 80.

challenge icon

Challenge

Medium

Change a setting according to its kind.

  1. Write local function processValue(config: Config, key: string): string that calls valueType(config, key) first.
  2. Return string.upper(value :: string) for a string, tostring((value :: number) * 10) for a number, otherwise "missing".
  3. Print processValue(settings, "theme") and processValue(settings, "maxUsers").

Press Run Code: the output ends with DARK and 1000.

Try it yourself

type Config = {[string]: string | number | boolean}

local settings: Config = {
    appName = "MyApp",
    debugMode = true,
    maxUsers = 100,
    theme = "dark",
}

local function valueType(config: Config, key: string): string
    local value = config[key]
    if value == nil then
        return "missing"
    end
    return typeof(value)
end

print(valueType(settings, "appName"))
print(valueType(settings, "debugMode"))
print(valueType(settings, "timeout"))
quiz iconTest yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

All lessons in Introduction To Luau

1Getting Started with Luau

What Is Luau?Why Use Luau?Your First Luau CodeType Checking & Error ModesRecap: Introduction to Luau

4Working with Functions

Typing Params & Return ValuesTyping Anonymous FunctionsFunctions Returning NothingOptional ParametersDefault Parameter ValuesDefaults for BooleansVariadic FunctionsDefining Function TypesRecap: Typed Functions

7Project: Typed Task Manager

Project: The Task ShapeFunction to Add a TaskProject lessonFunction to Change Task StatusProject lessonFunction: List Tasks by StatusProject lessonFunction: Print Task SummaryProject lessonCommand Loop: AddProject lessonCommand Loop: List and DoneProject lessonCommand Loop: SummaryProject lesson

10Project: Generic Inventory

Project: Inventory ItemFunction: Add ItemsProject lessonThe Weapons ListProject lessonFunction: Find Item By IDProject lessonSpecific Inventory TypesProject lessonFunction: Describe ItemsProject lessonAnswer Item QueriesProject lesson

2Core Types

Number, String and BooleanThe 'any' Type: Escape HatchThe 'unknown' TypeNil & Optional TypesType Inference in ActionExplicit Type AnnotationsRecap: Core Types Practice

5Aliases, Unions, Intersections

Type Aliases for PrimitivesUnion TypesWorking with Union TypesLiteral TypesIntersection TypesCombining Type AliasesRecap: Advanced Type Combos

8Enums, the Luau Way

The Enum Pattern in LuauNumeric Enums with TablesString Enums as UnionsUsing Literal Union EnumsFreezing Constant TablesRecap: Enums, the Luau Way

11Advanced Topics

Type AssertionsType Guards With typeofThe never TypeNil Safety In Strict ModeIndex SignaturesRecap: Config Value TypesRecap: Fine-Tuning Types

3Typed Tables: Arrays & Maps

Typed ArraysAdding and Reading ElementsWhat is a Map Type?Declaring and Accessing MapsIterating TablesMixed-Shape TablesReading a GridBuilding a Gridtable.unpackRecap: Arrays and Maps

6Typing Table Shapes

Inline Shape AnnotationsType Aliases for ShapesOptional PropertiesShapes vs. Loose TablesExtending ShapesAdding Methods to ShapesSelf and Colon MethodsRecap: Defining Table Shapes

9Generics: A First Look

The Problem Generics SolveA Generic Identity FunctionUsing a Generic FunctionGeneric ArraysGeneric Type AliasesRecap: Generic Functions

Practice on your own: Online Luau compiler