Enums

Similarities between Enums and Structs 

enum IpAddr {
    V4(u8, u8, u8, u8),
    V6(String),
}

let home = IpAddr::V4(127, 0, 0, 1);

let loopback = IpAddr::V6(String::from("::1"));

  • The name of each enum variant that we define also becomes a function that constructs an instance of the enum. 

    enum Message {
    Quit,
    Move { x: i32, y: i32 },
    Write(String),
    ChangeColor(i32, i32, i32),
}

    • Quit  has no data associated with it at all.

    • Move  has named fields, like a struct does.

    • Write  includes a single String .

    • ChangeColor  includes three i32  values.

  • We’re also able to define methods on enums using impl . 

    impl Message {
    fn call(&self) {
        // method body
    }
}

let m = Message::Write(String::from("hello"));
m.call();