User-Defined Types

Beyond built-in types, Compact allows you to define custom types to model your domain. This chapter covers the ways to create user-defined types:

Overview

Declaration	Purpose	Example
`struct Name { ... }`	Record with named fields	`struct Point { x: Field, y: Field }`
`enum Name { ... }`	Enumeration with variants	`enum Status { pending, approved }`

Structs group related data into a single type with named fields:

struct Player {
    address: Bytes<32>,
    score: Uint<64>,
    isActive: Boolean
}

Access fields with dot notation: player.score

Enums define a type with a fixed set of named values:

enum GameState { waiting, playing, finished }

Access variants with dot notation: GameState.waiting

⚠️ Important: Use dot notation (GameState.waiting), not Rust-style GameState::waiting.

To use custom types from TypeScript, export them:

export struct Player { ... }
export enum GameState { ... }