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# 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!
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