ALallengeorge·May 7, 2017
I really started looking into blanket implementations after I saw this example [1] in Tokio. Basically it says "implement the `AsyncRead` trait for any boxed type that implements `AsyncRead` or any `AsyncRead` trait object. The Error trait contains more examples [2].
As for "encapsulate ownership details". Hard to describe, but...let me point to Tokio [3] again. In Java if you wanted to share an IO reader/writer with two different objects you'd use the same type and pass the same reference to both owners. In Rust, the same idiom would require the wordy use of `Arc<Mutex<Type>>` or `Rc<RefCell<Type>>`. I hope we can both agree that that's frustrating. An alternative (as demonstrated by Tokio's `split` method) is to separate your base type into two other types - reader and writer - that can be owned independently. No more externally-visible
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ref counting. Of course, this isn't possible in all scenarios: there absolutely are times when you don't have a clean separation of types and have to ref count; but, avoid it if you can.
I learned all of this by poking into libs, asking a ton on the IRC channels (everyone is super friendly) and failing a lot. Any errors are my own. Hope that helps!
[1] https://github.com/tokio-rs/tokio-io/blob/master/src/lib.rs#...
[2] https://doc.rust-lang.org/src/std/error.rs.html#281
[3] https://github.com/tokio-rs/tokio-io/blob/master/src/lib.rs#...