---
url: /docs/logic/types.md
description: >-
  Define the shape of your data in Luna Park: every type of the type selector,
  object properties, type files, options, inferred and generated types, and
  default values.
---

# Data Types

Every value in Luna Park has a type: variables, properties, function inputs and outputs, store schemas, route inputs and outputs, database columns. Types make the editor offer the right inputs and nodes, color the pins of the graph, and generate typed code.

## The type selector

Next to the name of a value, the type selector (`Type...`) lists:

| Type | Value |
|---|---|
| **String** | Text.  |
| **Number** | A number, with or without decimals.  |
| **Boolean** | `true` or `false`.  |
| **Object** | Named properties, each with its own type: `{ name: String, age: Number }`. |
| **Record** | Any number of keys, all with the same type of value: a score per player name. The keys are String or Number. |
| **Interface** | An object of a built-in class, picked in a second list: **Date**, **URL**, **File**... Libraries and plugins add their own. |
| **Type** | A reference to a named type (see [Type files](#type-files)). |
| **Array** | An ordered list of values of the same type.  |
| **Combine** > **Union** | One of several types: a String or a Number. |
| **Combine** > **Intersection** | All of several object types, combined into one. |
| **Function** | A function, with its inputs (an Object) and its output. |
| **Void** | No value. Only for outputs: function outputs, events, computed values. |
| **Unknown** | Any value. |

Some places add their own entries: **Execute** for the execution pins of [macro](./scripts#function-settings) inputs and outputs, **Foreign Key** for [database columns](../backend-data/database#column-types).

Changing the type of a value resets what is specific to the old type (properties, item type...).

## Objects

Under an **Object**, the **+** button adds a property: give it a name and a type. Properties can be objects too, to any depth.

* Renaming a property keeps the logic and bindings that use it.
* Drag a property by its type selector to reorder it among its siblings.
* **×** removes it.
* `↑` and `↓` move between the name fields.

Some objects are partly locked: the parameters of a route, the automatic columns of a table.

## Type files

A **type** file holds named types, to define a shape once and use it everywhere. Create one with **New > Type** in the Explorer.

* **Add type** creates a type. Name it, then define it with the type selector.
* The **Preview code** button of a type shows its TypeScript definition.
* **×** deletes a type.

To use a named type, pick **Type** in any type selector, then the type in the list. The list also offers:

* each **Database**: the shape of one of its rows;
* each **Route**: its **Input body** or its **Output**.

A reference follows its target: when you change the type in its file, every value using it changes. Use them to keep the frontend and the backend in sync, for example by typing a variable with the **Output** of the route that fills it.

## Options

In type files, the options button next to a type (or a property) sets:

| Option | Effect |
|---|---|
| **Description** | Shown as a tooltip in forms and on the pins of the graph. |
| **Optional** | The value can be missing. Marked with `?`. Optional properties are left out of default values; add them from the **+** of the value form. |
| **Default** | The initial value. String, Number, and Boolean only. |
| **Format** | For String: `color` shows a color picker in value forms. `date-time` and `email` mark the expected format. |
| **Values** | The only allowed values, for String and Number. Value forms show them in a dropdown, and a String with values becomes a union of these texts in the generated code. |

Right-click any type selector to **Copy** a type, **Paste** it on another value, or open its **Options**.

## Infer and Generate

The type selector of function inputs and outputs, route outputs, and some node pins has two extra entries:

* **Infer** copies the type of the matching pin: the pin of the same name on the other side of the node, or the `response` of the route.
* **Generate** builds the type from a real value: run the logic once, then pick **Generate** to type a pin from the value it received. Handy for the response of an API called with `Fetch`.

## Values and defaults

The **Default** section of a component, the values of configuration files, and the values of nodes use forms built from the types:

* Basic types get a text field, a number field, a switch, a dropdown (with **Values**), or a color picker (with the `color` format).
* Arrays have a **+** to add items, and buttons to move or delete each item.
* Objects and records have a **+** to add keys. Click a key to rename it.
* Unknown and Union values let you pick the kind of value first.
* **Edit as JSON** edits an object or an array as JSON text. **Save** applies it.
* **Reset to default** puts back the **Default** of the type.
* **Generate with Sidekick** fills the value with example data, when [Sidekick](../workspace/sidekick) is connected.

## Types in the graph

The pins of the graph are colored by type: one color for String, Number, Boolean, objects, interfaces, and execution. Arrays have their own shape, with the color of their items. Unknown and union pins are neutral.

Hold `Ctrl + Alt` to show the name and the type of every pin. Connecting pins of incompatible types draws a red wire.