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36 lines
1.3 KiB
Rust
36 lines
1.3 KiB
Rust
/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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//! The `Castable` trait.
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use dom::bindings::conversions::get_dom_class;
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use dom::bindings::conversions::{DerivedFrom, IDLInterface};
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use dom::bindings::reflector::Reflectable;
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use std::mem;
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/// A trait to hold the cast functions of IDL interfaces that either derive
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/// or are derived from other interfaces.
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pub trait Castable: IDLInterface + Reflectable + Sized {
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/// Check whether a DOM object implements one of its deriving interfaces.
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fn is<T>(&self) -> bool where T: DerivedFrom<Self> {
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let class = unsafe {
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get_dom_class(self.reflector().get_jsobject().get()).unwrap()
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};
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T::derives(class)
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}
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/// Cast a DOM object upwards to one of the interfaces it derives from.
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fn upcast<T>(&self) -> &T where T: Castable, Self: DerivedFrom<T> {
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unsafe { mem::transmute(self) }
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}
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/// Cast a DOM object downwards to one of the interfaces it might implement.
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fn downcast<T>(&self) -> Option<&T> where T: DerivedFrom<Self> {
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if self.is::<T>() {
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Some(unsafe { mem::transmute(self) })
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} else {
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None
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}
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}
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}
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