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, }),
);

Trait DisplayCopy item path

§Completeness and parseability

§Internationalization

§Examples

Required Methods§

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

§Errors

§Examples

Implementors§

impl Display for AsciiChar

impl Display for Infallible

impl Display for FromBytesWithNulError

impl Display for IpAddr

impl Display for SocketAddr

impl Display for CheckedCastError

impl Display for PodCastError

impl Display for RoundingError

impl Display for Weekday

impl Display for comfy_wgpu::crossbeam::channel::RecvTimeoutError

impl Display for comfy_wgpu::crossbeam::channel::TryRecvError

impl Display for FontFamily

impl Display for TextStyle

impl Display for comfy_wgpu::egui::load::LoadError

impl Display for NumericColorSpace

impl Display for HexColor

impl Display for ComponentError

impl Display for QueryOneError

impl Display for ImageError

impl Display for ImageFormatHint

impl Display for comfy_wgpu::image::flat::Error

impl Display for CommandError

impl Display for comfy_wgpu::kira::manager::backend::cpal::Error

impl Display for AddClockError

impl Display for AddModulatorError

impl Display for AddSpatialSceneError

impl Display for AddSubTrackError

impl Display for FromFileError

impl Display for AddEmitterError

impl Display for AddListenerError

impl Display for SetRouteError

impl Display for Level

impl Display for LevelFilter

impl Display for EventLoopError

impl Display for ExternalError

impl Display for XNotSupported

impl Display for HandleError

impl Display for BadIcon

impl Display for CursorIcon

impl Display for CollectionAllocErr

impl Display for comfy_wgpu::smallvec::alloc::slice::GetDisjointMutError

impl Display for VarError

impl Display for std::fs::TryLockError

impl Display for ErrorKind

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

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

impl Display for ChmapPosition

impl Display for SelemChannelId

impl Display for alsa::pcm::Format

impl Display for LoadingError

impl Display for InsertWithKeyError

impl Display for calloop::error::Error

impl Display for codespan_reporting::files::Error

impl Display for BuildStreamError

impl Display for DefaultStreamConfigError

impl Display for DeviceNameError

impl Display for DevicesError

impl Display for PauseStreamError

impl Display for PlayStreamError

impl Display for StreamError

impl Display for SupportedStreamConfigsError

impl Display for SampleFormat

impl Display for DlError

impl Display for WgpuError

impl Display for Compression

impl Display for exr::error::Error

impl Display for gimli::read::Error

impl Display for gpu_alloc::error::AllocationError

impl Display for MapError

impl Display for gpu_descriptor::allocator::AllocationError

impl Display for humantime::date::Error

Trait Display