Example
use std::error::Error;
use std::fmt;
use std::convert::From;
use std::io::Error as IoError;
use std::str::Utf8Error;
#[derive(Debug)] // Allow the use of "{:?}" format specifier
enum CustomError {
Io(IoError),
Utf8(Utf8Error),
Other,
}
// Allow the use of "{}" format specifier
impl fmt::Display for CustomError {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
match *self {
CustomError::Io(ref cause) => write!(f, "I/O Error: {}", cause),
CustomError::Utf8(ref cause) => write!(f, "UTF-8 Error: {}", cause),
CustomError::Other => write!(f, "Unknown error!"),
}
}
}
// Allow this type to be treated like an error
impl Error for CustomError {
fn description(&self) -> &str {
match *self {
CustomError::Io(ref cause) => cause.description(),
CustomError::Utf8(ref cause) => cause.description(),
CustomError::Other => "Unknown error!",
}
}
fn cause(&self) -> Option<&Error> {
match *self {
CustomError::Io(ref cause) => Some(cause),
CustomError::Utf8(ref cause) => Some(cause),
CustomError::Other => None,
}
}
}
// Support converting system errors into our custom error.
// This trait is used in `try!`.
impl From<IoError> for CustomError {
fn from(cause: IoError) -> CustomError {
CustomError::Io(cause)
}
}
impl From<Utf8Error> for CustomError {
fn from(cause: Utf8Error) -> CustomError {
CustomError::Utf8(cause)
}
}
