Rust-Structs

struct1.rs

ColorClassicStruct is a named structure that contains three fields: red, green and blue. Each field has its own name, and we can access the values in the structure by using . For instance, we can use green.red to access red field of green structure.

ColorTupleStruct is a tuple structure that contains three elements but has no field names. And we can access the elements by using green.1 , green.0 and green.2.

In general, named structures provide clearer and more readable code because they explicitly identify each field name. Tuple structures are simpler and suitable for simple situation.

struct ColorClassicStruct {
    // TODO: Something goes here
    red: u8,
    green: u8,
    blue: u8,
}

struct ColorTupleStruct(u8, u8, u8);

#[derive(Debug)]
struct UnitLikeStruct;

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn classic_c_structs() {
        // TODO: Instantiate a classic c struct!
        // let green =
        let green = ColorClassicStruct {
            red: 0,
            green: 255,
            blue: 0
        };

        assert_eq!(green.red, 0);
        assert_eq!(green.green, 255);
        assert_eq!(green.blue, 0);
    }

    #[test]
    fn tuple_structs() {
        // TODO: Instantiate a tuple struct!
        // let green =
        let green = ColorTupleStruct(0, 255, 0);
        assert_eq!(green.0, 0);
        assert_eq!(green.1, 255);
        assert_eq!(green.2, 0);
    }

    #[test]
    fn unit_structs() {
        // TODO: Instantiate a unit-like struct!
        let unit_like_struct = UnitLikeStruct;
        let message = format!("{:?}s are fun!", unit_like_struct);

        assert_eq!(message, "UnitLikeStructs are fun!");
    }
}

struct2.rs

We create a new struct variable your_order that contains an instance of the Order structure with the same field values as order_template, but the values of name and count field are overridden with new values.

#[derive(Debug)]
struct Order {
    name: String,
    year: u32,
    made_by_phone: bool,
    made_by_mobile: bool,
    made_by_email: bool,
    item_number: u32,
    count: u32,
}

fn create_order_template() -> Order {
    Order {
        name: String::from("Bob"),
        year: 2019,
        made_by_phone: false,
        made_by_mobile: false,
        made_by_email: true,
        item_number: 123,
        count: 0,
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn your_order() {
        let order_template = create_order_template();
        // TODO: Create your own order using the update syntax and template above!
        // let your_order =
        let your_order = Order {
            name: "Hacker in Rust".to_string(),
            count: 1,
            ..order_template
        };
        assert_eq!(your_order.name, "Hacker in Rust");
        assert_eq!(your_order.year, order_template.year);
        assert_eq!(your_order.made_by_phone, order_template.made_by_phone);
        assert_eq!(your_order.made_by_mobile, order_template.made_by_mobile);
        assert_eq!(your_order.made_by_email, order_template.made_by_email);
        assert_eq!(your_order.item_number, order_template.item_number);
        assert_eq!(your_order.count, 1);
    }
}

Similar code in JavaScript

const orderTemplate = {
  name: 'Hacker in JavaScript',
  count: 2,
  discount: 0.1,
}

const yourOrder = {
  ...orderTemplate,
  name: 'Lambdas in JavaScript',
  count: 1,
}

console.log(yourOrder)

struct3.rs

This is so easy.

#[derive(Debug)]
struct Package {
    sender_country: String,
    recipient_country: String,
    weight_in_grams: i32,
}

impl Package {
    fn new(sender_country: String, recipient_country: String, weight_in_grams: i32) -> Package {
        if weight_in_grams <= 0 {
            panic!("Can not ship a weightless package.")
        } else {
            Package {
                sender_country,
                recipient_country,
                weight_in_grams,
            }
        }
    }

    fn is_international(&self) -> bool {
        // Something goes here...
        self.sender_country != self.recipient_country
    }

    fn get_fees(&self, cents_per_gram: i32) -> i32 {
        // Something goes here...
        self.weight_in_grams * cents_per_gram
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    #[should_panic]
    fn fail_creating_weightless_package() {
        let sender_country = String::from("Spain");
        let recipient_country = String::from("Austria");

        Package::new(sender_country, recipient_country, -2210);
    }

    #[test]
    fn create_international_package() {
        let sender_country = String::from("Spain");
        let recipient_country = String::from("Russia");

        let package = Package::new(sender_country, recipient_country, 1200);

        assert!(package.is_international());
    }

    #[test]
    fn create_local_package() {
        let sender_country = String::from("Canada");
        let recipient_country = sender_country.clone();

        let package = Package::new(sender_country, recipient_country, 1200);

        assert!(!package.is_international());
    }

    #[test]
    fn calculate_transport_fees() {
        let sender_country = String::from("Spain");
        let recipient_country = String::from("Spain");

        let cents_per_gram = 3;

        let package = Package::new(sender_country, recipient_country, 1500);

        assert_eq!(package.get_fees(cents_per_gram), 4500);
        assert_eq!(package.get_fees(cents_per_gram * 2), 9000);
    }
}