Enums - Rust By Example
Description: A description

# Enums

The `enum` keyword allows the creation of a type which may be one of a few different variants. Any variant which is valid as a `struct` is also valid as an `enum`.

    // An attribute to hide warnings for unused code.
    #![allow(dead_code)]

    // Create an `enum` to classify a web event. Note how both
    // names and type information together specify the variant:
    // `PageLoad != PageUnload` and `KeyPress(char) != Paste(String)`.
    // Each is different and independent.
    enum WebEvent {
        // An `enum` may either be `unit-like`,
        PageLoad,
        PageUnload,
        // like tuple structs,
        KeyPress(char),
        Paste(String),
        // or like structures.
        Click { x: i64, y: i64 },
    }

    // A function which takes a `WebEvent` enum as an argument and
    // returns nothing.
    fn inspect(event: WebEvent) {
        match event {
            WebEvent::PageLoad => println!("page loaded"),
            WebEvent::PageUnload => println!("page unloaded"),
            // Destructure `c` from inside the `enum`.
            WebEvent::KeyPress(c) => println!("pressed '{}'.", c),
            WebEvent::Paste(s) => println!("pasted \"{}\".", s),
            // Destructure `Click` into `x` and `y`.
            WebEvent::Click { x, y } => {
                println!("clicked at x={}, y={}.", x, y);
            },
        }
    }

    fn main() {
        let pressed = WebEvent::KeyPress('x');
        // `to_owned()` creates an owned `String` from a string slice.
        let pasted  = WebEvent::Paste("my text".to_owned());
        let click   = WebEvent::Click { x: 20, y: 80 };
        let load    = WebEvent::PageLoad;
        let unload  = WebEvent::PageUnload;

        inspect(pressed);
        inspect(pasted);
        inspect(click);
        inspect(load);
        inspect(unload);
    }

### See also:

`attributes`, `match`, `fn`, and `String`