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android / platform / external / rust / crates / downcast / refs/heads/android15-tests-dev
commit8f15941fddf8fdbb80eb29743207880673911df4[log] [tgz]
authorXin Li <[email protected]>Tue Jun 18 11:43:34 2024 -0700
committerXin Li <[email protected]>Tue Jun 18 11:43:34 2024 -0700
tree2ed307f637804d94ea18b6a3a96038c19f43f839
parentfb9fcc10964b99e960bf1a3a004f968665a89a58 [diff]
parent70259aaf25cdfa3eb845d01e41589a22f4035eb9 [diff]
Mark ab/11976889 as merged in aosp-main-future

Bug: 347831320
Merged-In: Icf55148f9eaf8e9dd89ab13248dace62c9cc3a1c
Change-Id: Id13fe8e0d0a12ca937233e9365f9849b5517ec39
tree: 2ed307f637804d94ea18b6a3a96038c19f43f839
  1. examples/
  2. src/
  3. tests/
  4. LICENSE ⇨ LICENSE-MIT
  5. .cargo_vcs_info.json
  6. .gitattributes
  7. .gitignore
  8. Android.bp
  9. Cargo.toml
  10. cargo_embargo.json
  11. clippy.toml
  12. LICENSE-MIT
  13. METADATA
  14. MODULE_LICENSE_MIT
  15. OWNERS
  16. README.md
README.md

downcast   Latest Version

A trait (& utilities) for downcasting trait objects back to their original types.

link to API documentation

example usage

Add to your Cargo.toml:

[dependencies]
downcast = "0.12"

Add to your crate root:

#[macro_use]
extern crate downcast;
  • simple showcases the most simple usage of this library.
  • with_params showcases how to deal with traits who have type parameters.
  • sync_service 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!