Struct with a generic trait which is also a generic trait

Question

In Rust 1.15, I have created a trait to abstract over reading & parsing file format(s). I\'m trying to create a struct which has this generic trait inside.

I hav

Answer 1

You probably don't want a type parameter, you want an associated type:

use std::io::Read;

trait MyReader {
    type R: Read;

    fn new(Self::R) -> Self;
    fn into_inner(self) -> Self::R;

    fn get_next(&mut self) -> Option;
    fn do_thingie(&mut self);
}

struct MyIterThing<'a, T>
    where T: MyReader + 'a
{
    inner: &'a mut T,
}

fn main() {}

See also:

• When is it appropriate to use an associated type versus a generic type?
• Why am I getting "parameter is never used [E0392]"?
• How can I have an unused type parameter in a struct?