Struct

fn main() {
    let mut user1 = User {
        email: String::from("someone@example.com"),
        username: String::from("someusername123"),
        active: true,
        sign_in_count: 1,
    };
    user1.email = String::from("anotheremail@example.com");
}

return a struct

struct User {
    //...
}

fn build_user() -> User {
    User {
        //...
    }
}

fn main() {
    let user1 = build_user(...);
}

Merge tow struct

fn main() {
    let user1 = User {
         // ....
        };

    let user2 = User {
        email: String::from("another@example.com"),
        ..user1
    };
}

struct as tuple

struct Color(i32, i32, i32);
struct Point(i32, i32, i32);

fn main() {
    let black = Color(0, 0, 0);
    let origin = Point(0, 0, 0);
}

Ownership of Struct Data

we used the owned String type rather than the &str string slice type. for that data to be valid for as long as the entire struct is valid.

to store references to data owned by something else, it's require to use the lifetimes, to ensure the data referenced by a struct is valid for as long as the struct is.

Methode with struct

struct Rectangle {
   width: u32,
   height: u32,
}

// snip ...
impl Rectangle {
    fn area(&self) -> u32 {
        self.width * self.height
    }
    fn can_hold(&self, other: &Rectangle) -> bool {
        self.width > other.width && self.height > other.height
    }
}

fn main() {
   let rect1 = Rectangle {
       width: 30,
       height: 50,
   };
  let rect2 = Rectangle {
      width: 10,
      height: 40,
  };

   println!(
       "The area of the rectangle is {} square pixels.",
       rect1.area()
   );
   println!("Can rect1 hold rect2? {}", rect1.can_hold(&rect2));
}

enum

enum IpAddrKind {
    V4,
    V6,
}

fn main() {
    let four = IpAddrKind::V4;
    let six = IpAddrKind::V6;

    route(IpAddrKind::V4);
    route(IpAddrKind::V6);
}

fn route(ip_kind: IpAddrKind) {}

Enum with struct

fn main() {
    enum IpAddrKind {
        V4,
        V6,
    }

    struct IpAddr {
        kind: IpAddrKind,
        address: String,
    }

    let home = IpAddr {
        kind: IpAddrKind::V4,
        address: String::from("127.0.0.1"),
    };

    let loopback = IpAddr {
        kind: IpAddrKind::V6,
        address: String::from("::1"),
    };
}

Enum as args as tuple

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

    let home     = IpAddr::V4(127, 0, 0, 1);
    let loopback = IpAddr::V6(String::from("::1"));
}

Example

enum Coin {
    Penny,
    Nickel,
    Dime,
    Quarter,
}

fn value_in_cents(coin: Coin) -> u8 {
    match coin {
        Coin::Penny => 1,
        Coin::Nickel => 5,
        Coin::Dime => 10,
        Coin::Quarter => 25,
    }
}

fn main() {
    value_in_cents(Coin::Quarter(UsState::Alaska));
}

how to use value_in_cents:
- how to call it
- how to receive return value, is there always the same type u8,int...
- tow to send and enum or one variant from enum

with if, the expression needs to return a Boolean value, but here, it can return any type. The type of coin in this example is the Coin enum

#[derive(Debug)] // so we can inspect the state in a minute
enum UsState {
    Alabama,
    Alaska,
    // --snip--
}

enum Coin {
    Penny,
    Nickel,
    Dime,
    Quarter(UsState),
}

fn main() {}

Ayoub docs