Match

The match expression in Cairo allows us to control the flow of our code by comparing a felt252 data type or an enum against various patterns and then running specific code based on the pattern that matches.

For example:

#[derive(Drop, Serde)]
enum Colour {
    Red,
    Blue,
    Green,
    Orange,
    Black,
}
 
#[derive(Drop, Serde)]
enum Coin {
    Penny,
    Nickel,
    Dime,
    Quarter,
}
 
fn value_in_cents(coin: Coin) -> felt252 {
    match coin {
        Coin::Penny => 1,
        Coin::Nickel => 5,
        Coin::Dime => 10,
        Coin::Quarter => 25,
    }
}
 
fn specified_colour(colour: Colour) -> felt252 {
    let mut response: felt252 = '';
 
    match colour {
        Colour::Red => { response = 'You passed in Red'; },
        Colour::Blue => { response = 'You passed in Blue'; },
        Colour::Green => { response = 'You passed in Green'; },
        Colour::Orange => { response = 'You passed in Orange'; },
        Colour::Black => { response = 'You passed in Black'; },
    };
 
    response
}
 
fn quiz(num: felt252) -> felt252 {
    let mut response: felt252 = '';
 
    match num {
        0 => { response = 'You failed' },
        _ => { response = 'You Passed' },
    };
 
    response
}