ParamsBuilder

Here is something modeled losely after std::task::Task. The goal is to provide default parameters, named parameters and a random order of providing paramaters before doing something with it.

#[deriving(Eq)]
struct ParamsBuilder {
    foo: uint,
    bar: ~str,
    baz: uint,
    run: bool
}

impl ParamsBuilder {
  fn default() -> ParamsBuilder{
    ParamsBuilder { foo: 0, bar: ~"", baz: 0, run: false }
  }

  fn foo(mut self, foo: uint) -> ParamsBuilder {
    self.foo = foo;
    self
  }

  fn bar(mut self, bar: ~str) -> ParamsBuilder {
    self.bar = bar;
    self
  }

  fn baz(mut self, baz: uint) -> ParamsBuilder {
    self.baz = baz;
    self
  }

  fn run(mut self) -> ParamsBuilder {
    self.run = true;
    println!("{:?}", self);
    self
  }
}


#[test]
fn test_chain(){
  let params = ParamsBuilder::default().foo(1).bar(~"bar").baz(2).run();

  assert_eq!(ParamsBuilder { foo: 1, bar: ~"bar", baz: 2, run: true }, params);
}

Thanks to Yurume for the help on this.

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