# Struct ethcore_util::standard::io::Error 1.0.0 [−] [src]

    pub struct Error { /* fields omitted */ }

The error type for I/O operations of the `Read`, `Write`, `Seek`, and associated traits.

Errors mostly originate from the underlying OS, but custom instances of `Error` can be created with crafted error messages and a particular value of `ErrorKind`.

## Methods

### `impl Error`

#### `fn new<E>(kind: ErrorKind, error: E) -> Error where E: Into<Box<Error + 'static + Send + Sync>>`

Creates a new I/O error from a known kind of error as well as an arbitrary error payload.

This function is used to generically create I/O errors which do not originate from the OS itself. The `error` argument is an arbitrary payload which will be contained in this `Error`.

# Examples

    use std::io::{Error, ErrorKind};

    // errors can be created from strings
    let custom_error = Error::new(ErrorKind::Other, "oh no!");

    // errors can also be created from other errors
    let custom_error2 = Error::new(ErrorKind::Interrupted, custom_error);

#### `fn last_os_error() -> Error`

Returns an error representing the last OS error which occurred.

This function reads the value of `errno` for the target platform (e.g. `GetLastError` on Windows) and will return a corresponding instance of `Error` for the error code.

# Examples

    use std::io::Error;

    println!("last OS error: {:?}", Error::last_os_error());

#### `fn from_raw_os_error(code: i32) -> Error`

Creates a new instance of an `Error` from a particular OS error code.

# Examples

On Linux:

    use std::io;

    let error = io::Error::from_raw_os_error(98);
    assert_eq!(error.kind(), io::ErrorKind::AddrInUse);

On Windows:

    use std::io;

    let error = io::Error::from_raw_os_error(10048);
    assert_eq!(error.kind(), io::ErrorKind::AddrInUse);

#### `fn raw_os_error(&self) -> Option<i32>`

Returns the OS error that this error represents (if any).

If this `Error` was constructed via `last_os_error` or `from_raw_os_error`, then this function will return `Some`, otherwise it will return `None`.

# Examples

    use std::io::{Error, ErrorKind};

    fn print_os_error(err: &Error) {
        if let Some(raw_os_err) = err.raw_os_error() {
            println!("raw OS error: {:?}", raw_os_err);
        } else {
            println!("Not an OS error");
        }
    }

    fn main() {
        // Will print "raw OS error: ...".
        print_os_error(&Error::last_os_error());
        // Will print "Not an OS error".
        print_os_error(&Error::new(ErrorKind::Other, "oh no!"));
    }

#### `fn get_ref(&self) -> Option<&Error + 'static + Send + Sync>`
1.3.0

Returns a reference to the inner error wrapped by this error (if any).

If this `Error` was constructed via `new` then this function will return `Some`, otherwise it will return `None`.

# Examples

    use std::io::{Error, ErrorKind};

    fn print_error(err: &Error) {
        if let Some(inner_err) = err.get_ref() {
            println!("Inner error: {:?}", inner_err);
        } else {
            println!("No inner error");
        }
    }

    fn main() {
        // Will print "No inner error".
        print_error(&Error::last_os_error());
        // Will print "Inner error: ...".
        print_error(&Error::new(ErrorKind::Other, "oh no!"));
    }

#### `fn get_mut(&mut self) -> Option<&mut Error + 'static + Send + Sync>`
1.3.0

Returns a mutable reference to the inner error wrapped by this error (if any).

If this `Error` was constructed via `new` then this function will return `Some`, otherwise it will return `None`.

# Examples

    use std::io::{Error, ErrorKind};
    use std::{error, fmt};
    use std::fmt::Display;

    #[derive(Debug)]
    struct MyError {
        v: String,
    }

    impl MyError {
        fn new() -> MyError {
            MyError {
                v: "oh no!".to_owned()
            }
        }

        fn change_message(&mut self, new_message: &str) {
            self.v = new_message.to_owned();
        }
    }

    impl error::Error for MyError {
        fn description(&self) -> &str { &self.v }
    }

    impl Display for MyError {
        fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
            write!(f, "MyError: {}", &self.v)
        }
    }

    fn change_error(mut err: Error) -> Error {
        if let Some(inner_err) = err.get_mut() {
            inner_err.downcast_mut::<MyError>().unwrap().change_message("I've been changed!");
        }
        err
    }

    fn print_error(err: &Error) {
        if let Some(inner_err) = err.get_ref() {
            println!("Inner error: {}", inner_err);
        } else {
            println!("No inner error");
        }
    }

    fn main() {
        // Will print "No inner error".
        print_error(&change_error(Error::last_os_error()));
        // Will print "Inner error: ...".
        print_error(&change_error(Error::new(ErrorKind::Other, MyError::new())));
    }

#### `fn into_inner(self) -> Option<Box<Error + 'static + Send + Sync>>`
1.3.0

Consumes the `Error`, returning its inner error (if any).

If this `Error` was constructed via `new` then this function will return `Some`, otherwise it will return `None`.

# Examples

    use std::io::{Error, ErrorKind};

    fn print_error(err: Error) {
        if let Some(inner_err) = err.into_inner() {
            println!("Inner error: {}", inner_err);
        } else {
            println!("No inner error");
        }
    }

    fn main() {
        // Will print "No inner error".
        print_error(Error::last_os_error());
        // Will print "Inner error: ...".
        print_error(Error::new(ErrorKind::Other, "oh no!"));
    }

#### `fn kind(&self) -> ErrorKind`

Returns the corresponding `ErrorKind` for this error.

# Examples

    use std::io::{Error, ErrorKind};

    fn print_error(err: Error) {
        println!("{:?}", err.kind());
    }

    fn main() {
        // Will print "No inner error".
        print_error(Error::last_os_error());
        // Will print "Inner error: ...".
        print_error(Error::new(ErrorKind::AddrInUse, "oh no!"));
    }

## Trait Implementations

### `impl Display for Error`

#### `fn fmt(&self, fmt: &mut Formatter) -> Result<(), Error>`

Formats the value using the given formatter.

### `impl Debug for Error`

#### `fn fmt(&self, __arg_0: &mut Formatter) -> Result<(), Error>`

Formats the value using the given formatter.

### `impl Error for Error`

#### `fn description(&self) -> &str`

A short description of the error. Read more

#### `fn cause(&self) -> Option<&Error>`

The lower-level cause of this error, if any. Read more

### `impl From<NulError> for Error`

#### `fn from(NulError) -> Error`

Performs the conversion.

### `impl<W> From<IntoInnerError<W>> for Error`

#### `fn from(iie: IntoInnerError<W>) -> Error`

Performs the conversion.

### `impl From<ErrorKind> for Error`
1.14.0

Intended for use for errors not exposed to the user, where allocating onto the heap (for normal construction via Error::new) is too costly.

#### `fn from(kind: ErrorKind) -> Error`

Performs the conversion.

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