rust

rust-class-method-and-trait.rs

// file_1.rs
//
// implement class method and instance method with the same name
//
struct Car {
  stamp: &'static str
}
impl Car {
  fn print() {
    println!("It is Car class method!")
  }
}

trait Print {
  fn print(&self) -> ();
}
impl Print for Car {
  fn print(&self) {
    println!("It is Car instance method")
  }
}

fn main() {
  let car = Car { stamp: "BMW" };
  Car::print();
  car.print();
}

// file_2.rs
//
// traits couldn't implement class methods
// but could implement class methods which return Self (because with
// type it knows what implementation should use)
//
struct Car {
  stamp: &'static str
}
impl Car {
  fn print(&self) {
    println!("It is Car instance with stamp: {}", self.stamp)
  }
}

trait Face {
  fn print() -> ();
  fn new(var: &'static str) -> Self;
}
impl Face for Car {
  fn print() {
    println!("It is Car class method!")
  }
  fn new(var: &'static str) -> Car {
    Car { stamp: var }
  }
}

fn main() {
  // Car::print();               // first-class methods are not supported
  // Face::print();              // cannot determine a type for this bounded type parameter: unconstrained type
  // let car = Face::new("BMV"); // cannot determine a type for this bounded type parameter: unconstrained type

  let car: Car = Face::new("BMV");
  car.print();
}