Struct trait_map::TypedContext

pub struct TypedContext<'a, E: ?Sized> { /* private fields */ }

Stores concrete type for an entry inside a TraitMap

It can be upcast to an untyped Context using the .upcast() method.

Implementations

impl<'a, Entry> TypedContext<'a, Entry>where
Entry: 'static,

pub fn upcast(self) -> Context<'a>

Convert back into an untyped Context.

pub fn add_trait<Trait>(&mut self) -> &mut Selfwhere
Trait: ?Sized + Pointee<Metadata = DynMetadata<Trait>> + 'static,
Entry: Unsize<Trait>,

Add a trait to the type map. This method is idempotent, so adding a trait multiple times will only register it once.

By default, every type is associated with the TraitMapEntry trait.

Examples

impl TraitMapEntry for MyStruct {
  fn on_create<'a>(&mut self, context: Context<'a>) {
    context
     .downcast::<Self>()
     .add_trait::<dyn ExampleTrait>()
     .add_trait::<dyn ExampleTraitTwo>();
  }
}

pub fn remove_trait<Trait>(&mut self) -> &mut Selfwhere
Trait: ?Sized + Pointee<Metadata = DynMetadata<Trait>> + 'static,
Entry: Unsize<Trait>,

Remove a trait from the type map. This method is idempotent, so removing a trait multiple times is a no-op.

By default, every type is associated with the TraitMapEntry trait. As such, this trait cannot be removed from an entry. Trying to call .remove_trait::<dyn TraitMapEntry>() is a no-op.

Examples

impl TraitMapEntry for MyStruct {
  // ...

  fn on_update<'a>(&mut self, context: Context<'a>) {
    context
     .downcast::<Self>()
     .remove_trait::<dyn ExampleTrait>()
     .remove_trait::<dyn ExampleTraitTwo>();
  }
}

pub fn has_trait<Trait>(&self) -> boolwhere
Trait: ?Sized + Pointee<Metadata = DynMetadata<Trait>> + 'static,
Entry: Unsize<Trait>,

Test if the trait is registered with the type map.

Examples

impl TraitMapEntry for MyStruct {
  // ...

  fn on_update<'a>(&mut self, context: Context<'a>) {
    let mut context = context.downcast::<Self>();
    if !context.has_trait::<dyn ExampleTrait>() {
      context.add_trait<dyn ExampleTrait>();
    }
  }
}

Trait Implementations

impl<'a, E: Debug + ?Sized> Debug for TypedContext<'a, E>

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

Formats the value using the given formatter.