![]() Definition of MyTrait, a data provider. As &mut dyn Any, there is also the downcastmut method, for getting a mutable reference to the inner value. egui runs on the web, natively, and in your favorite game engine (or will soon). As &dyn Any (a borrowed trait object), it has the is and downcastref methods, to test if the contained value is of a given type, and to get a reference to the inner value as a type. Logger function for any type that implements Debug. egui is a simple, fast, and highly portable immediate mode gui library for rust. pub fn downcast (self) -> Result < Box , Box where T: Any, Attempt to downcast the box to a concrete type.This can be avoided byĬonverting the smart pointer into a &dyn Any instead, which will return type_id() on the value will produce the TypeId of theĬontainer, not the underlying trait object. One piece of behavior to keep in mind when using Any as a trait object,Ä®specially with types like Box or Arc, is that simplyĬalling. The purpose of the Any trait is to make it possible to pass around values of any type and dynamically downcast. Note that &dyn Any is limited to testing whether a value is of a specifiedĬoncrete type, and cannot be used to test whether a type implements a trait. Im not sure what you mean about trait names. See the Box documentation for the full details. that of the Error itself) and contravariant lifetime to the largest ( static ). The implementation would need to squash the covariant parameters to their smallest possible lifetimes (i.e. Box adds the downcast method, which attempts toĬonvert to a Box. After reading about the issue, it seems like downcasting really should work for any type unless that type has invariant lifetime parameters. Is also the downcast_mut method, for getting a mutable reference to the ![]() As &dyn Any (a borrowed trait object), it has the isĪnd downcast_ref methods, to test if the contained value is of a given type,Īnd to get a reference to the inner value as a type. Any and TypeIdĪny itself can be used to get a TypeId, and has more features when usedĪs a trait object. By calling downcast () you pass the type to which it should downcase, the TypeID of the requested type will be compared with the TypeID stored inside the trait object and if thats true the trait object will be interpreted as the requested type. For me, each such example shows both the power of Rust and the difficulty of really mastering the language. To downcast a trait to a concrete type the concrete type must be known (at compile time). Provider trait and accompanying API, which enable trait objects to provideÄata based on typed requests, an alternate form of runtime reflection. Is it possible to downcast an Rc to an Rc Hereâs the background with as many details elided as possible.downcast 0.11.0 Docs. Of any 'static type through runtime reflection. API documentation for the Rust Any trait in crate downcast. This module contains the Any trait, which enables dynamic typing ![]()
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