Methods on tuples and enums

In Rust, methods cannot only be defined on structs, they can also be defined on tuples and enums, and even on built-in types like integers.

Here is an example of an instance method mood defined on the variants of an Day enum. It matches the variant to print out the mood string of the day:

// see code in Chapter 6/code/method_enum.rs 
enum Day {   
    Monday, 
    Tuesday, 
    Wednesday, 
    Thursday, 
    Friday, 
    Saturday, 
    Sunday, 
} 
 
impl Day { 
    fn mood(&self) { 
        println!("{}", match *self { 
            Day::Friday => "it's friday!", 
            Day::Saturday | Day::Sunday => "weekend :-)", 
            _ => "weekday...", 
        }) 
    } 
} 
 
fn main() { 
    let today = Day::Tuesday; 
    today.mood(); 
} 

This prints out the following output:

weekday...