compio::buf::bumpalo::core_alloc::fmt

Trait Display

1.36.0 · Source

pub trait Display {
    // Required method
    fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>;
}

Expand description

Format trait for an empty format, {}.

Implementing this trait for a type will automatically implement the ToString trait for the type, allowing the usage of the .to_string() method. Prefer implementing the Display trait for a type, rather than ToString.

Display is similar to Debug, but Display is for user-facing output, and so cannot be derived.

For more information on formatters, see the module-level documentation.

§Completeness and parseability

Display for a type might not necessarily be a lossless or complete representation of the type. It may omit internal state, precision, or other information the type does not consider important for user-facing output, as determined by the type. As such, the output of Display might not be possible to parse, and even if it is, the result of parsing might not exactly match the original value.

However, if a type has a lossless Display implementation whose output is meant to be conveniently machine-parseable and not just meant for human consumption, then the type may wish to accept the same format in FromStr, and document that usage. Having both Display and FromStr implementations where the result of Display cannot be parsed with FromStr may surprise users.

§Internationalization

Because a type can only have one Display implementation, it is often preferable to only implement Display when there is a single most “obvious” way that values can be formatted as text. This could mean formatting according to the “invariant” culture and “undefined” locale, or it could mean that the type display is designed for a specific culture/locale, such as developer logs.

If not all values have a justifiably canonical textual format or if you want to support alternative formats not covered by the standard set of possible formatting traits, the most flexible approach is display adapters: methods like str::escape_default or Path::display which create a wrapper implementing Display to output the specific display format.

§Examples

Implementing Display on a type:

use std::fmt;

struct Point {
    x: i32,
    y: i32,
}

impl fmt::Display for Point {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "({}, {})", self.x, self.y)
    }
}

let origin = Point { x: 0, y: 0 };

assert_eq!(format!("The origin is: {origin}"), "The origin is: (0, 0)");

Required Methods§

1.0.0 · Source

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

§Errors

This function should return Err if, and only if, the provided Formatter returns Err. String formatting is considered an infallible operation; this function only returns a Result because writing to the underlying stream might fail and it must provide a way to propagate the fact that an error has occurred back up the stack.

§Examples

use std::fmt;

struct Position {
    longitude: f32,
    latitude: f32,
}

impl fmt::Display for Position {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "({}, {})", self.longitude, self.latitude)
    }
}

assert_eq!(
    "(1.987, 2.983)",
    format!("{}", Position { longitude: 1.987, latitude: 2.983, }),
);

Implementors§

§

impl Display for SerdeJsonCodecError

Display

Trait Display Copy item path

§Completeness and parseability

§Internationalization

§Examples

Required Methods§

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

§Errors

§Examples

Implementors§

impl Display for SerdeJsonCodecError

impl Display for ConfigError

impl Display for ConnectError

impl Display for compio::quic::ConnectionError

impl Display for compio::quic::ReadError

impl Display for ReadExactError

impl Display for StoppedError

impl Display for compio::quic::WriteError

impl Display for compio::quic::h3::error::ConnectionError

impl Display for StreamError

impl Display for ErrorOrigin

impl Display for FrameError

impl Display for SettingsError

impl Display for HeaderError

impl Display for ConnectionErrorIncoming

impl Display for StreamErrorIncoming

impl Display for EarlyDataError

impl Display for VerifierBuilderError

impl Display for CertificateError

impl Display for compio::tls::rustls::Error

impl Display for ExtendedKeyPurpose

impl Display for compio::tls::rustls::pki_types::pem::Error

impl Display for EncodeError

impl Display for EncryptError

impl Display for compio::ws::tungstenite::Error

impl Display for Message

impl Display for compio::ws::tungstenite::error::CapacityError

impl Display for ProtocolError

impl Display for SubProtocolError

impl Display for TlsError

impl Display for UrlError

impl Display for CloseCode

impl Display for Control

impl Display for Data

impl Display for OpCode

impl Display for ReserveError

impl Display for ReserveExactError

impl Display for compio::buf::bumpalo::core_alloc::slice::GetDisjointMutError

impl Display for AsciiChar

impl Display for Infallible

impl Display for FromBytesWithNulError

impl Display for IpAddr

impl Display for SocketAddr

impl Display for VarError

impl Display for std::fs::TryLockError

impl Display for std::io::error::ErrorKind

impl Display for std::sync::mpsc::RecvTimeoutError

impl Display for std::sync::mpsc::TryRecvError

impl Display for log::Level

impl Display for log::LevelFilter

impl Display for Value

impl Display for BernoulliError

impl Display for rand::distr::uniform::Error

impl Display for rand::distr::weighted::Error

impl Display for bool

impl Display for char

impl Display for f16

impl Display for f32

impl Display for f64

impl Display for i8

impl Display for i16

impl Display for i32

impl Display for i64

impl Display for i128

impl Display for isize

impl Display for !

impl Display for str

impl Display for u8

impl Display for u16

impl Display for u32

Trait Display