Can I get a trait object of a multi-trait instance without using a generic type?

by

You can create an empty trait that merges those two traits:

use std::io::{Read, Seek};

trait SeekRead: Seek + Read {}
impl<T: Seek + Read> SeekRead for T {}

fn user_dynamic(stream: &mut SeekRead) {}

This will create a new vtable for SeekRead that contains all the function pointers of both Seek and Read.

You will not be able to cast your &mut SeekRead to either &mut Seek or &mut Read without some trickery (see Why doesn’t Rust support trait object upcasting?)

More Related Contents:

  1. What is the correct way to return an Iterator (or any other trait)?
  2. Temporarily move out of borrowed content
  3. Initialize a large, fixed-size array with non-Copy types
  4. Sending trait objects between threads in Rust
  5. Why would I implement methods on a trait instead of as part of the trait?
  6. How to initialize struct fields which reference each other
  7. Is it possible to make a type only movable and not copyable?
  8. How can this instance seemingly outlive its own parameter lifetime?
  9. How to use struct self in member method closure
  10. How do I call a function through a member variable?
  11. How do you pass a Rust function as a parameter?
  12. Why does removing return give me an error: expected type `()` but found type
  13. How do I implement a trait with a generic method?
  14. Linking the lifetimes of self and a reference in method
  15. Is there a way to create a function pointer to a method in Rust?
  16. How do I use conditional compilation with `cfg` and Cargo?
  17. When I can use either Cell or RefCell, which should I choose?
  18. Return an async function from a function in Rust
  19. How to implement `serde::Serialize` for a boxed trait object?
  20. Borrow two mutable values from the same HashMap
  21. Can I take a byte array and deserialize it into a struct?
  22. How do I create a Rust callback function to pass to a FFI function?
  23. Is there any difference between matching on a reference to a pattern or a dereferenced value?
  24. Why does a lazy-static value claim to not implement a trait that it clearly implements?
  25. How do I convert a usize to a u32 using TryFrom?
  26. Borrow pointer errors recursively traversing tree [duplicate]
  27. How can I borrow from a HashMap to read and write at the same time?
  28. Comparing every element in a vector with the next one
  29. How to repeat a static string at compile time
  30. How to concatenate static strings in Rust

Leave a Comment