| # downcast   ![Latest Version] |
| |
| [Latest Version]: https://img.shields.io/crates/v/downcast.svg |
| |
| A trait (& utilities) for downcasting trait objects back to their original types. |
| |
| ## [link to API documentation](https://docs.rs/downcast) |
| |
| ## example usage |
| |
| Add to your Cargo.toml: |
| |
| ```toml |
| [dependencies] |
| downcast = "0.12" |
| ``` |
| |
| Add to your crate root: |
| |
| ```rust |
| #[macro_use] |
| extern crate downcast; |
| ``` |
| |
| * [simple](examples/simple.rs) showcases the most simple usage of this library. |
| * [with_params](examples/with_params.rs) showcases how to deal with traits who have type parameters. |
| * [sync_service](examples/sync_service.rs) showcases how to downcast `Arc`-pointers. |
| |
| ## build features |
| |
| * **std (default)** enables all functionality requiring the standard library (`Downcast::downcast()`). |
| * **nightly** enables all functionality requiring rust nightly (`Any::type_name()`). |
| |
| ## faq |
| |
| __Q: I'm getting `the size for values of type XXX cannot be known at compile time` errors, what am i doing wrong?__ |
| |
| A: Make sure you use the corresponding `Any` bound along with the `Downcast` traits. So, `Any` for `Downcast` and `AnySync` for `DowncastSync`. |
| |
| __Q: Can i cast trait objects to trait objects?__ |
| |
| A: No, that is currently no possible in safe rust - and unsafe solutions are very tricky, as well. If you found a solution, feel free to share it! |
| |
| __Q: What is the difference between this and the `downcast-rs` crate on crates.io?__ |
| |
| A: At the moment, there isn't one, really. |
| There was an unfortunate naming clash. You may consider using the other crate, as it is more actively maintained. |
| This one is considered feature-complete and frozen in functionality. |
| Hopefully, one day, the Rust language will make downcasting easier and we will need neither of these crates anymore! |
