Trait std::error::Error 1.0.0[−][src]
pub trait Error: Debug + Display { fn description(&self) -> &str { ... } fn cause(&self) -> Option<&Error> { ... } }
Error is a trait representing the basic expectations for error values,
i.e. values of type E in Result<T, E>. Errors must describe
themselves through the Display and Debug traits, and may provide
cause chain information:
The cause method is generally used when errors cross "abstraction
boundaries", i.e. when a one module must report an error that is "caused"
by an error from a lower-level module. This setup makes it possible for the
high-level module to provide its own errors that do not commit to any
particular implementation, but also reveal some of its implementation for
debugging via cause chains.
Provided Methods
fn description(&self) -> &str
This method is soft-deprecated.
Although using it won’t cause compilation warning,
new code should use Display instead
and new impls can omit it.
To obtain error description as a string, use to_string().
Examples
match "xc".parse::<u32>() { Err(e) => { // Print `e` itself, not `e.description()`. println!("Error: {}", e); } _ => println!("No error"), }Run
fn cause(&self) -> Option<&Error>
The lower-level cause of this error, if any.
Examples
use std::error::Error; use std::fmt; #[derive(Debug)] struct SuperError { side: SuperErrorSideKick, } impl fmt::Display for SuperError { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { write!(f, "SuperError is here!") } } impl Error for SuperError { fn description(&self) -> &str { "I'm the superhero of errors" } fn cause(&self) -> Option<&Error> { Some(&self.side) } } #[derive(Debug)] struct SuperErrorSideKick; impl fmt::Display for SuperErrorSideKick { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { write!(f, "SuperErrorSideKick is here!") } } impl Error for SuperErrorSideKick { fn description(&self) -> &str { "I'm SuperError side kick" } } fn get_super_error() -> Result<(), SuperError> { Err(SuperError { side: SuperErrorSideKick }) } fn main() { match get_super_error() { Err(e) => { println!("Error: {}", e.description()); println!("Caused by: {}", e.cause().unwrap()); } _ => println!("No error"), } }Run
Methods
impl Error + 'static[src]
impl Error + 'staticpub fn is<T: Error + 'static>(&self) -> bool1.3.0[src]
pub fn is<T: Error + 'static>(&self) -> boolReturns true if the boxed type is the same as T
pub fn downcast_ref<T: Error + 'static>(&self) -> Option<&T>1.3.0[src]
pub fn downcast_ref<T: Error + 'static>(&self) -> Option<&T>Returns some reference to the boxed value if it is of type T, or
None if it isn't.
pub fn downcast_mut<T: Error + 'static>(&mut self) -> Option<&mut T>1.3.0[src]
pub fn downcast_mut<T: Error + 'static>(&mut self) -> Option<&mut T>Returns some mutable reference to the boxed value if it is of type T, or
None if it isn't.
impl Error + Send + 'static[src]
impl Error + Send + 'staticpub fn is<T: Error + 'static>(&self) -> bool1.3.0[src]
pub fn is<T: Error + 'static>(&self) -> boolForwards to the method defined on the type Any.
pub fn downcast_ref<T: Error + 'static>(&self) -> Option<&T>1.3.0[src]
pub fn downcast_ref<T: Error + 'static>(&self) -> Option<&T>Forwards to the method defined on the type Any.
pub fn downcast_mut<T: Error + 'static>(&mut self) -> Option<&mut T>1.3.0[src]
pub fn downcast_mut<T: Error + 'static>(&mut self) -> Option<&mut T>Forwards to the method defined on the type Any.
impl Error + Send + Sync + 'static[src]
impl Error + Send + Sync + 'staticpub fn is<T: Error + 'static>(&self) -> bool1.3.0[src]
pub fn is<T: Error + 'static>(&self) -> boolForwards to the method defined on the type Any.
pub fn downcast_ref<T: Error + 'static>(&self) -> Option<&T>1.3.0[src]
pub fn downcast_ref<T: Error + 'static>(&self) -> Option<&T>Forwards to the method defined on the type Any.
pub fn downcast_mut<T: Error + 'static>(&mut self) -> Option<&mut T>1.3.0[src]
pub fn downcast_mut<T: Error + 'static>(&mut self) -> Option<&mut T>Forwards to the method defined on the type Any.
impl Error[src]
impl Errorpub fn downcast<T: Error + 'static>(
self: Box<Self>
) -> Result<Box<T>, Box<Error>>1.3.0[src]
pub fn downcast<T: Error + 'static>(
self: Box<Self>
) -> Result<Box<T>, Box<Error>>Attempt to downcast the box to a concrete type.
impl Error + Send[src]
impl Error + Sendpub fn downcast<T: Error + 'static>(
self: Box<Self>
) -> Result<Box<T>, Box<Error + Send>>1.3.0[src]
pub fn downcast<T: Error + 'static>(
self: Box<Self>
) -> Result<Box<T>, Box<Error + Send>>Attempt to downcast the box to a concrete type.
impl Error + Send + Sync[src]
impl Error + Send + Syncpub fn downcast<T: Error + 'static>(
self: Box<Self>
) -> Result<Box<T>, Box<Self>>1.3.0[src]
pub fn downcast<T: Error + 'static>(
self: Box<Self>
) -> Result<Box<T>, Box<Self>>Attempt to downcast the box to a concrete type.
Implementations on Foreign Types
impl Error for TryFromSliceError[src]
impl Error for TryFromSliceErrorImplementors
impl Error for VarErrorimpl Error for JoinPathsErrorimpl Error for !impl Error for AllocErrimpl Error for LayoutErrimpl Error for CannotReallocInPlaceimpl Error for ParseBoolErrorimpl Error for Utf8Errorimpl Error for ParseIntErrorimpl Error for TryFromIntErrorimpl Error for ParseFloatErrorimpl Error for FromUtf8Errorimpl Error for FromUtf16Errorimpl Error for ParseErrorimpl Error for DecodeUtf16Errorimpl<T: Error> Error for Box<T>impl Error for std::fmt::Errorimpl Error for BorrowErrorimpl Error for BorrowMutErrorimpl Error for CharTryFromErrorimpl Error for ParseCharErrorimpl Error for NulErrorimpl Error for FromBytesWithNulErrorimpl Error for IntoStringErrorimpl<W: Send + Debug> Error for IntoInnerError<W>impl Error for std::io::Errorimpl Error for CharsErrorimpl Error for AddrParseErrorimpl Error for StripPrefixErrorimpl<T: Send> Error for SendError<T>impl<T: Send> Error for TrySendError<T>impl Error for RecvErrorimpl Error for TryRecvErrorimpl Error for RecvTimeoutErrorimpl Error for SystemTimeErrorimpl<T> Error for PoisonError<T>impl<T> Error for TryLockError<T>