Structs & Enums

Structs

Define structured data types with the struct keyword:

struct User {
    name: string
    email: string
    age: int
}

Creating Instances

user = User{
    name: "Alice",
    email: "alice@example.com",
    age: 30
}

Accessing Fields

io.println(user.name)   // "Alice"
user.age = 31            // Update field

Methods

Attach methods to structs using dot-syntax:

User.display() -> string {
    return "${self.name} <${self.email}>"
}

io.println(user.display())  // "Alice <alice@example.com>"

Methods have an implicit self parameter referring to the instance.

Visibility

Structs are private by default. Use pub to export:

pub struct Config {
    host: string
    port: int
}

Methods inherit the visibility of their type.

Enums

Define enumerations:

enum Color {
    Red
    Green
    Blue
}

enum Status {
    Active
    Inactive
    Pending(string)  // Variant with data
}

Using Enums

color = Color.Red
status = Status.Pending("awaiting review")

Pattern Matching on Enums

match color {
    Color.Red => io.println("Red"),
    Color.Green => io.println("Green"),
    Color.Blue => io.println("Blue")
}

The compiler warns if a match on an enum is not exhaustive.

Enum with Data

enum Result {
    Ok(string)
    Error(string)
}

match result {
    Result.Ok(value) => io.println("Got: ${value}"),
    Result.Error(msg) => io.println("Error: ${msg}")
}

Type Aliases

Create aliases for existing types:

type UserID = int
type Headers = map[string]string

Composition over Inheritance

Haira has no classes or inheritance. Use struct composition:

struct Address {
    street: string
    city: string
}

struct Employee {
    name: string
    address: Address
    salary: float
}

employee = Employee{
    name: "Bob",
    address: Address{street: "123 Main", city: "NYC"},
    salary: 75000.0
}