object-provider

This crate provides the ObjectProvider trait and related types to support dynamic type-directed object lookups. See the documentation for more details.

lib.rs:

Trait for requesting values by type from a given object.

Examples

Using a Provider

let provider: &dyn ObjectProvider;

// It's possible to request concrete types like `PathBuf`
let path_buf = provider.request_ref::<PathBuf>().unwrap();
assert_eq!(path_buf, my_path);

// Requesting `!Sized` types, like slices and trait objects, is also supported.
let path = provider.request_ref::<Path>().unwrap();
assert_eq!(path, my_path);

let debug = provider.request_ref::<dyn Debug>().unwrap();
assert_eq!(
    format!("{:?}", debug),
    format!("{:?}", my_path),
);

// Types or interfaces not explicitly provided return `None`.
assert!(provider.request_ref::<i32>().is_none());
assert!(provider.request_ref::<dyn AsRef<Path>>().is_none());

Implementing a Provider

struct MyProvider {
    path: PathBuf,
}

impl ObjectProvider for MyProvider {
    fn provide<'a>(&'a self, request: Pin<&mut Request<'a>>) {
        request
            .provide_ref::<PathBuf>(&self.path)
            .provide_ref::<Path>(&self.path)
            .provide_ref::<dyn Debug>(&self.path);
    }
}