Trait Display

1.0.0 · 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.

§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, }),
);

Trait DisplayCopy item path

§Internationalization

§Examples

Required Methods§

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

§Errors

§Examples

Implementors§

impl Display for geng_core::prelude::bincode::ErrorKind

impl Display for BernoulliError

impl Display for WeightedError

impl Display for geng_core::prelude::futures::io::ErrorKind

impl Display for AsciiChar

impl Display for Infallible

impl Display for FromBytesWithNulError

impl Display for core::net::ip_addr::IpAddr

impl Display for SocketAddr

impl Display for GetDisjointMutError

impl Display for VarError

impl Display for std::fs::TryLockError

impl Display for RecvTimeoutError

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

impl Display for DecodeError

impl Display for CheckedCastError

impl Display for PodCastError

impl Display for RoundingError

impl Display for Weekday

impl Display for claxon::error::Error

impl Display for BuildStreamError

impl Display for DefaultFormatError

impl Display for DeviceNameError

impl Display for DevicesError

impl Display for PauseStreamError

impl Display for PlayStreamError

impl Display for StreamError

impl Display for SupportedFormatsError

impl Display for MatchingType

impl Display for gif::encoder::EncodingError

impl Display for gif::reader::decoder::DecodingError

impl Display for gimli::read::Error

impl Display for ContextError

impl Display for CreationError

impl Display for hound::Error

impl Display for GetTimezoneError

impl Display for ImageError

impl Display for ImageFormatHint

impl Display for image::flat::Error

impl Display for jpeg_decoder::error::Error

impl Display for AudioReadError

impl Display for VorbisError

impl Display for HeaderReadError

impl Display for libloading::error::Error

impl Display for minimp3::error::Error

impl Display for nix::Error

impl Display for Errno

impl Display for Signal

impl Display for InetAddr

impl Display for nix::sys::socket::addr::IpAddr

impl Display for SockAddr

impl Display for OggReadError

impl Display for BlendOp

impl Display for DisposeOp

impl Display for png::decoder::stream::DecodingError

impl Display for png::encoder::EncodingError

impl Display for DecoderError

impl Display for ErrorCode

impl Display for rusttype::Error

impl Display for CacheReadErr

impl Display for CacheWriteErr

impl Display for CollectionAllocErr

impl Display for TiffError

impl Display for TiffFormatError

impl Display for TiffUnsupportedError

impl Display for FaceParsingError

impl Display for Void

impl Display for ConnectError

impl Display for GlobalError

impl Display for MessageParseError

impl Display for MessageWriteError

impl Display for LzwError

Trait Display