---
title: Classes
description: Unified data and behavior with Java-style organization and Rust-powered execution.
icon: Shapes
---

Classes in Mist bridge the gap between Java's organizational structure and Rust's performance. They group fields, constructors, and methods within a single cohesive block, using C-style method signatures with `&self` for the instance parameter.

## Basic Syntax

A class groups fields and methods together. Fields use semicolons and the `Type name` convention. Methods use C-style syntax with `&self` as the first parameter for shared access.

```mist
pub class Logger {
    String prefix;

    pub void info(&self, message str&) {
        self.log(LogLevel::Info, message);
    }

    void log(&self, LogLevel level, message str&) {
        println!("{level} {} {}", self.prefix, message);
    }
}
```

## The Constructor

Mist uses the explicit `constructor` keyword for initialization:

```mist
pub constructor() {
    self.prefix = "default".to_string();
}
```

Constructors can take parameters:

```mist
pub constructor(String prefix) {
    self.prefix = prefix;
}
```

## Instance Methods & `&self`

Methods use `&self` (shared reference) or `&mut self` (mutable reference) as the first parameter.

```mist
pub void warning(&self, message str&) {
    self.log(LogLevel::Warning, message);
}

pub void reset(&mut self) {
    self.prefix = String::new();
}
```

## Inheritance

Classes support single inheritance with the `:` syntax. Use `super = Super::new()` in the constructor to call the parent constructor. Override methods by placing `override(Parent)` after the parameter list.

```mist
pub class Animal {
    pub String name;

    constructor() {
        self.name = "Rex".to_string();
    }

    pub String speak(&self) {
        "Unknown".to_string()
    }
}

pub class Dog : Animal {
    constructor() {
        super = Super::new();
    }

    pub String speak(&self) override(Animal) {
        "Woof!".to_string()
    }
}
```

## Trait Implementations

Traits can be implemented directly inside a class body:

```mist
pub class Dog : Animal {
    constructor() {
        self.name = name;
    }

    pub String speak(&self) override(Animal) {
        "Woof!".to_string()
    }

    impl std::fmt::Display {
        Result<(), std::fmt::Error> fmt(&self, std::fmt::Formatter<'_> mut& f) {
            write!(f, "🐾 {}", self.name)
        }
    }
}
```

## Generics

Classes support generic type parameters:

```mist
pub class Container<T> {
    T value;

    constructor(T val) {
        self.value = val;
    }

    pub &T get(&self) {
        &self.value
    }
}
```

## Key Characteristics

- **Unified Scope**: Data and behavior live in one class block.
- **C-Style Methods**: Return type before name — no `fn` keyword.
- **`&self` Parameter**: The self reference is explicit and uses `&` syntax.
- **Inheritance**: Single inheritance with `override(Parent)` for polymorphic dispatch.
- **Encapsulation**: Visibility modifiers (`pub`) control API exposure.
- **Inline Impl**: Traits can be implemented directly within the class body.
- **Zero-Cost Classes**: Under the hood, Mist desugars these into idiomatic Rust structs and implementation blocks.