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android / platform / external / rust / crates / downcast / 46697198d609f156775a0863bbd449e3ec84be67
commit46697198d609f156775a0863bbd449e3ec84be67[log] [tgz]
authorMartin Geisler <[email protected]>Wed Nov 15 16:47:11 2023 +0100
committerMartin Geisler <[email protected]>Mon Dec 11 10:22:10 2023 +0000
treeff176214b85e9271e57b726f443643ddc3042b27
parent21be4635b1b8eabdf7a3abed6367ada2e24be5c6 [diff]
Import 'downcast' crate

Request Document: go/android-rust-importing-crates
For CL Reviewers: go/android3p#cl-review
For Build Team: go/ab-third-party-imports
Bug: http://b/310600230

Change-Id: I68fb2495b218f6b930072e2ee052402036c3d56e
IGNORE_COMPLIANCELINT=LicenseIsKnown: I believe the symlink is triggering b/270248598
18 files changed
tree: ff176214b85e9271e57b726f443643ddc3042b27
  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!