Trait CastNone

pub trait CastNone: Sized {
    type Inner;

    // Required methods
    fn and_downcast<T: ObjectType>(self) -> Option<T>
       where Self::Inner: MayDowncastTo<T>;
    fn and_downcast_ref<T: ObjectType>(&self) -> Option<&T>
       where Self::Inner: MayDowncastTo<T>;
    fn and_upcast<T: ObjectType>(self) -> Option<T>
       where Self::Inner: IsA<T>;
    fn and_upcast_ref<T: ObjectType>(&self) -> Option<&T>
       where Self::Inner: IsA<T>;
    fn and_dynamic_cast<T: ObjectType>(self) -> Result<T, Self>;
    fn and_dynamic_cast_ref<T: ObjectType>(&self) -> Option<&T>;
}

Convenience trait mirroring Cast, implemented on Option<Object> types.

Warning

Inevitably this trait will discard information about a downcast failure: you don’t know if the object was not of the expected type, or if it was None. If you need to handle the downcast error, use Cast over a glib::Object.

Example

let widget: Option<Widget> = list_item.child();

// Without using `CastNone`
let label = widget.unwrap().downcast::<gtk::Label>().unwrap();

// Using `CastNone` we can avoid the first `unwrap()` call
let label = widget.and_downcast::<gtk::Label>().unwrap();

Required Associated Types

type Inner

Required Methods

fn and_downcast<T: ObjectType>(self) -> Option<T>

where Self::Inner: MayDowncastTo<T>,

fn and_downcast_ref<T: ObjectType>(&self) -> Option<&T>

where Self::Inner: MayDowncastTo<T>,

fn and_upcast<T: ObjectType>(self) -> Option<T>

where Self::Inner: IsA<T>,

fn and_upcast_ref<T: ObjectType>(&self) -> Option<&T>

where Self::Inner: IsA<T>,

fn and_dynamic_cast<T: ObjectType>(self) -> Result<T, Self>

fn and_dynamic_cast_ref<T: ObjectType>(&self) -> Option<&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<I: ObjectType + Sized> CastNone for Option<I>

type Inner = I

fn and_downcast<T: ObjectType>(self) -> Option<T>

where Self::Inner: MayDowncastTo<T>,

fn and_downcast_ref<T: ObjectType>(&self) -> Option<&T>

where Self::Inner: MayDowncastTo<T>,

fn and_upcast<T: ObjectType>(self) -> Option<T>

where Self::Inner: IsA<T>,

fn and_upcast_ref<T: ObjectType>(&self) -> Option<&T>

where Self::Inner: IsA<T>,

fn and_dynamic_cast<T: ObjectType>(self) -> Result<T, Self>

fn and_dynamic_cast_ref<T: ObjectType>(&self) -> Option<&T>

Implementors