Trait tor_rpcbase::ObjectRefExt

pub trait ObjectRefExt {
    // Required method
    fn cast_to_trait<T: ?Sized + 'static>(&self) -> Option<&T>;
}

Extension trait for dyn Object and similar to support convenient downcasting to dyn Trait.

You don’t need to use this for downcasting to an object’s concrete type; for that, use downcast_rs::DowncastSync.

Examples

use tor_rpcbase::{decl_object, Object, ObjectRefExt};
use std::sync::Arc;
pub struct Frog {}
pub trait HasFeet {
    fn num_feet(&self) -> usize;
}
impl HasFeet for Frog {
    fn num_feet(&self) -> usize { 4 }
}
// Have `Frog` implement Object and declare that it can be
// downcast to HasFeet.
decl_object!{ Frog : [HasFeet] }

/// If `obj` is a HasFeet, return how many feet it has.
/// Otherwise, return 0.
fn check_feet(obj: Arc<dyn Object + 'static>) -> usize {
    let maybe_has_feet: Option<&dyn HasFeet> = obj.cast_to_trait();
    match maybe_has_feet {
        Some(foot_haver) => foot_haver.num_feet(),
        None => 0,
    }
}

assert_eq!(check_feet(Arc::new(Frog{})), 4);

Required Methods

fn cast_to_trait<T: ?Sized + 'static>(&self) -> Option<&T>

Try to cast this Object to a T. On success, return a reference to T; on failure, return None.

Implementations on Foreign Types

impl ObjectRefExt for Arc<dyn Object>

fn cast_to_trait<T: ?Sized + 'static>(&self) -> Option<&T>

Implementors

impl ObjectRefExt for dyn Object