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", so this trait is not object safe.

Implementations on Foreign Types

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>

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: 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>

Implementors