Trait ObjectArcExt

pub trait ObjectArcExt {
    // Required methods
    fn cast_to_trait<T: ?Sized + 'static>(&self) -> Option<&T>;
    fn cast_to_arc_trait<T: ?Sized + 'static>(
        self,
    ) -> Result<Arc<T>, Arc<dyn Object>>;
}

Extension trait for Arc<dyn Object> 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::{Object, ObjectArcExt, templates::*};
use derive_deftly::Deftly;
use std::sync::Arc;

#[derive(Deftly)]
#[derive_deftly(Object)]
#[deftly(rpc(downcastable_to = "HasFeet"))]
pub struct Frog {}
pub trait HasFeet {
    fn num_feet(&self) -> usize;
}
impl HasFeet for Frog {
    fn num_feet(&self) -> usize { 4 }
}

/// If `obj` is a HasFeet, return how many feet it has.
/// Otherwise, return 0.
fn check_feet(obj: Arc<dyn Object>) -> 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 Arc<dyn Object> to a T. On success, return a reference to T; on failure, return None.

fn cast_to_arc_trait<T: ?Sized + 'static>( self, ) -> Result<Arc<T>, Arc<dyn Object>>

Try to cast this Arc<dyn Object> to an Arc<T>.

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementations on Foreign Types

impl ObjectArcExt for Arc<dyn Object>

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

fn cast_to_arc_trait<T: ?Sized + 'static>( self, ) -> Result<Arc<T>, Arc<dyn Object>>

Implementors