builder_prototype.rs

#[deriving(Show, Clone, PartialEq)]
struct City<'a> {
  name: &'a str,
  country: &'a str
}

impl<'a> City<'a> {
  fn prototype() -> City<'a> {
    City { name: "", country: "" }
  }

  fn name(mut self, name: &'a str) -> City {
    self.name = name;
    self
  }

  fn country(mut self, country: &'a str) -> City {
    self.country = country;
    self
  }
}

#[test]
fn city() {
  let city = City::prototype();
  let berlin = City::prototype().name("Berlin").country("Germany");

  assert_eq!(city, City { name: "", country: "" });
  assert_eq!(berlin, City { name: "Berlin", country: "Germany" });
}