MultiAny

multi_any

Trait MultiAny 

Source 
pub trait MultiAny: Any {
    // Required method
    fn get_metadata(&self, type_id: TypeId) -> Option<Meta>;
}
Expand description

A trait for dynamic typing that allows downcasting to both concrete types and trait objects.

Similar to std::any::Any, but supports downcasting to traits implemented by the type.

Most users should implement this trait via the #[derive(MultiAny)] macro.

§Examples

use multi_any::*;

// Traits must be annotated with `#[multi_any]`
// With "nightly" feature this is not required
#[multi_any]
trait Trait1 {}
#[multi_any]
trait Trait2 {}

// MultiAny can be derived, and implemented traits must be specified
#[derive(MultiAny)]
#[multi_any(Trait1, Trait2)]
struct Foo;

impl Trait1 for Foo {}
impl Trait2 for Foo {}

// convert Box<Foo> to Box<dyn MultiAny>
let foo: Box<dyn MultiAny> = Box::new(Foo);

// downcast to concrete type
let foo_ref: &Foo = foo.downcast_ref().unwrap();

// downcast to trait object
let trait_ref = foo.downcast_ref::<dyn Trait1>().unwrap();

// downcast to Box
let foo: Box<dyn Trait1> = foo.downcast().unwrap();

Required Methods§

Source

fn get_metadata(&self, type_id: TypeId) -> Option<Meta>

Returns type-erased metadata for the requested type.

§Parameters
  • type_id: The TypeId of the requested type or trait object.
§Returns
  • Some(Meta) if the type matches the concrete type or a trait implemented by the object.
  • None if the type does not match.

Implementors must ensure that the returned Meta matches the actual data type and metadata type.

Implementations§

Source§

impl dyn MultiAny

Source

pub fn downcast_ref<RequestedType>(&self) -> Option<&RequestedType>
where RequestedType: Pointee + ?Sized + 'static, RequestedType::Metadata: TypedMetadata,

Attempts to downcast a MultiAny object to a reference of type RequestedType.

Returns Some(&RequestedType) if the object can be interpreted as the requested type, or None otherwise.

§Type Parameters
  • RequestedType: The concrete type or trait object to downcast to.
§Panics
  • Can panic with invalid implementation of get_metadata (Derived implementation is guaranteed to be valid.)
Source

pub fn downcast_mut<RequestedType>(&mut self) -> Option<&mut RequestedType>
where RequestedType: Pointee + ?Sized + 'static, RequestedType::Metadata: TypedMetadata,

Attempts to downcast a MultiAny object to a mutable reference of type RequestedType.

Returns Some(&mut RequestedType) if the object can be interpreted as the requested type, or None otherwise.

§Type Parameters
  • RequestedType: The concrete type or trait object to downcast to.
§Panics
  • Can panic with invalid implementation of get_metadata (Derived implementation is guaranteed to be valid.)
Source

pub fn downcast<RequestedType>( self: Box<Self>, ) -> Result<Box<RequestedType>, Box<Self>>
where RequestedType: Pointee + ?Sized + 'static, RequestedType::Metadata: TypedMetadata,

Attempts to downcast a Box<dyn MultiAny> to a Box<RequestedType>.

Returns Ok(Box<RequestedType>) if the object can be interpreted as the requested type, or Err(Box<dyn MultiAny>) otherwise. This is a consuming operation.

§Type Parameters
  • RequestedType: The concrete type or trait object to downcast to.
§Panics
  • Can panic with invalid implementation of get_metadata (Derived implementation is guaranteed to be valid.)

Trait Implementations§

Source§

impl Debug for dyn MultiAny

Source§

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter. Read more

Implementors§