Struct

Demo: struct-demo

• It groups multiple items of mixed data types.

• Each item in a struct has a name.

struct Shuttle {
    name: String,
    crew_size: u16,
    fuel: f64,
}

To use struct data type:

// create a variable
let car = Shuttle {
    name: String::from("Car"),
    crew_size: 11,
    fuel: 1.0,
};

// access a field of the variable
println!("{}", car.name);

Struct Update syntax

We can create another Shuttle by using the existing one.

let bus = Shuttle {
    name: String::from("Bus"),
    ..car
};

Be careful, name must be a new String because of the ownship.

let bus = Shuttle {
    ..car
};
// Error: The name's ownship on car is moved to bus. Car has no name.

Struct Method

impl Shuttle {
    fn get_name(&self) -> &str {
        &self.name
    }
}

• The methods are written inside impl, not struct.

• The first parameter of the method must be the reference of the structure itself, &self.

We can implement a "setter" function, too.

impl Shuttle {
    fn add_fuel(&mut self, amount: f64) {
        self.fuel += amount;
    }
}

Associated function

Associated function lives with struct, too. But, it hasn't &self parameter. So it can't access the fields in struct.

It's commonly used for "constructor".

impl Shuttle {
    fn new(name: &str) -> Shuttle {
      Shuttle {
          name: String::from(name),
          crew_size: 0,
          fuel: 0.0,
      }
  }
}

// use the new function in Shuttle
let ship = Shuttle::new("Ship");

Tuple Struct

It's just alike the normal tuple, but it also has a name like struct.

struct Color(u8, u8, u8);

// use it
let red = Color(255, 0, 0);

// access the first item
println!("{}", red.0); // same as a tuple

// pass a reference of Color variable to a function
fn get_red_value(color: &Color) -> u8 {
    color.0
}