Trait gdk_pixbuf::Cast

pub trait Cast: ObjectType {
    pub fn upcast<T>(self) -> T
    where
        Self: IsA<T>,
        T: ObjectType,
    { ... }
    pub fn upcast_ref<T>(&self) -> &T
    where
        Self: IsA<T>,
        T: ObjectType,
    { ... }
    pub fn downcast<T>(self) -> Result<T, Self>
    where
        Self: CanDowncast<T>,
        T: ObjectType,
    { ... }
    pub fn downcast_ref<T>(&self) -> Option<&T>
    where
        Self: CanDowncast<T>,
        T: ObjectType,
    { ... }
    pub fn dynamic_cast<T>(self) -> Result<T, Self>
    where
        T: ObjectType,
    { ... }
    pub fn dynamic_cast_ref<T>(&self) -> Option<&T>
    where
        T: ObjectType,
    { ... }
    pub unsafe fn unsafe_cast<T>(self) -> T
    where
        T: ObjectType,
    { ... }
    pub unsafe fn unsafe_cast_ref<T>(&self) -> &T
    where
        T: ObjectType,
    { ... }
}

Upcasting and downcasting support.

Provides conversions up and down the class hierarchy tree.

Provided methods

pub fn upcast<T>(self) -> T where
    Self: IsA<T>,
    T: ObjectType, 

Upcasts an object to a superclass or interface T.

NOTE: This statically checks at compile-time if casting is possible. It is not always known at compile-time, whether a specific object implements an interface or not, in which case upcast would fail to compile. dynamic_cast can be used in these circumstances, which is checking the types at runtime.

Example

let button = gtk::Button::new();
let widget = button.upcast::<gtk::Widget>();

pub fn upcast_ref<T>(&self) -> &T where
    Self: IsA<T>,
    T: ObjectType, 

Upcasts an object to a reference of its superclass or interface T.

NOTE: This statically checks at compile-time if casting is possible. It is not always known at compile-time, whether a specific object implements an interface or not, in which case upcast would fail to compile. dynamic_cast can be used in these circumstances, which is checking the types at runtime.

Example

let button = gtk::Button::new();
let widget = button.upcast_ref::<gtk::Widget>();

pub fn downcast<T>(self) -> Result<T, Self> where
    Self: CanDowncast<T>,
    T: ObjectType, 

Tries to downcast to a subclass or interface implementor T.

Returns Ok(T) if the object is an instance of T and Err(self) otherwise.

NOTE: This statically checks at compile-time if casting is possible. It is not always known at compile-time, whether a specific object implements an interface or not, in which case upcast would fail to compile. dynamic_cast can be used in these circumstances, which is checking the types at runtime.

Example

let button = gtk::Button::new();
let widget = button.upcast::<gtk::Widget>();
assert!(widget.downcast::<gtk::Button>().is_ok());

pub fn downcast_ref<T>(&self) -> Option<&T> where
    Self: CanDowncast<T>,
    T: ObjectType, 

Tries to downcast to a reference of its subclass or interface implementor T.

Returns Some(T) if the object is an instance of T and None otherwise.

NOTE: This statically checks at compile-time if casting is possible. It is not always known at compile-time, whether a specific object implements an interface or not, in which case upcast would fail to compile. dynamic_cast can be used in these circumstances, which is checking the types at runtime.

Example

let button = gtk::Button::new();
let widget = button.upcast::<gtk::Widget>();
assert!(widget.downcast_ref::<gtk::Button>().is_some());

pub fn dynamic_cast<T>(self) -> Result<T, Self> where
    T: ObjectType, 

Tries to cast to an object of type T. This handles upcasting, downcasting and casting between interface and interface implementors. All checks are performed at runtime, while downcast and upcast will do many checks at compile-time already.

It is not always known at compile-time, whether a specific object implements an interface or not, and checking as to be performed at runtime.

Returns Ok(T) if the object is an instance of T and Err(self) otherwise.

Example

let button = gtk::Button::new();
let widget = button.dynamic_cast::<gtk::Widget>();
assert!(widget.is_ok());
let widget = widget.unwrap();
assert!(widget.dynamic_cast::<gtk::Button>().is_ok());

pub fn dynamic_cast_ref<T>(&self) -> Option<&T> where
    T: ObjectType, 

Tries to cast to reference to an object of type T. This handles upcasting, downcasting and casting between interface and interface implementors. All checks are performed at runtime, while downcast and upcast will do many checks at compile-time already.

It is not always known at compile-time, whether a specific object implements an interface or not, and checking as to be performed at runtime.

Returns Some(T) if the object is an instance of T and None otherwise.

Example

let button = gtk::Button::new();
let widget = button.dynamic_cast_ref::<gtk::Widget>();
assert!(widget.is_some());
let widget = widget.unwrap();
assert!(widget.dynamic_cast_ref::<gtk::Button>().is_some());

pub unsafe fn unsafe_cast<T>(self) -> T where
    T: ObjectType, 

Casts to T unconditionally.

Panics if compiled with debug_assertions and the instance doesn’t implement T.

pub unsafe fn unsafe_cast_ref<T>(&self) -> &T where
    T: ObjectType, 

Casts to &T unconditionally.

Panics if compiled with debug_assertions and the instance doesn’t implement T.

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Implementors

impl<T> Cast for T where
    T: ObjectType, 

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