Trait ObjectOrVariantHelper 

pub trait ObjectOrVariantHelper<T, U> {
    // Required methods
    fn convert_to_dest_type_helper(object: &T) -> Option<&U>;
    fn convert_to_dest_type_helper_mut(object: &mut T) -> Option<&mut U>;
}

This trait is a helper trait for implementing ObjectOrVariant indirectly in child crates.

To implement ObjectOrVariant for type U in a child crate, you need to implement ObjectOrVariantHelper for PhantomData<U>.

This is necessary because Rust does not support impl<T> ForeignTrait<LocalType> for T

But Rust does support impl<T> ForeignTrait<LocalType> for ForeignType<T>

Details can be found in here.

Therefore, we cannot implement ObjectOrVariant directly using impl<U: TraitBound> ObjectOrVariant<LocalType> for U

but we can do impl<U: TraitBound> ObjectOrVariantHelper<LocalType, U> for PhantomData<U>

There is an indirection to get rid of PhantomData<U> because we want to have a clean API for pool methods where you can pass in U directly instead of PhantomData<U>.

Required Methods

fn convert_to_dest_type_helper(object: &T) -> Option<&U>

fn convert_to_dest_type_helper_mut(object: &mut T) -> Option<&mut U>

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementations on Foreign Types

impl<T: NodeTrait> ObjectOrVariantHelper<Node, T> for PhantomData<T>

fn convert_to_dest_type_helper(node: &Node) -> Option<&T>

fn convert_to_dest_type_helper_mut(node: &mut Node) -> Option<&mut T>

impl<T> ObjectOrVariantHelper<T, T> for PhantomData<T>

fn convert_to_dest_type_helper(object: &T) -> Option<&T>

fn convert_to_dest_type_helper_mut(object: &mut T) -> Option<&mut T>

impl<T> ObjectOrVariantHelper<UiNode, T> for PhantomData<T>

where T: Control,

fn convert_to_dest_type_helper(node: &UiNode) -> Option<&T>

fn convert_to_dest_type_helper_mut(node: &mut UiNode) -> Option<&mut T>

Implementors