chain_body.rs

    use std::io::{self,Read};
    use std::borrow::Borrow;
    use iron::response::{WriteBody,ResponseBody};

    pub struct BodyChain<T, U>(pub T, pub U);

    impl <T: WriteBody, U: WriteBody> WriteBody for BodyChain<T, U> {
        fn write_body(&mut self, res: &mut ResponseBody) -> io::Result<()> {
            let &mut BodyChain(ref mut a, ref mut b) = self;
            a.write_body(res).and_then(|_| b.write_body(res))
        }
    }

    pub fn chain_body<T,U,TO,UO>(a: U, b: T) -> Box<WriteBody + Send> where
        T: ToOwned<Owned=TO>,
        U: ToOwned<Owned=UO>,
        TO: WriteBody + Borrow<T> + Send + 'static,
        UO: WriteBody + Borrow<U> + Send + 'static
    {
        Box::new(BodyChain(a.to_owned(), b.to_owned()))
    }