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.

§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, }),
);

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 &dyn Show

impl Display for ShownJobStatus

impl Display for tag2upload_service_manager::db_migration::Outcome

impl Display for NotForUsReason

impl Display for OracleTaskError

impl Display for ProcessingError

impl Display for StartupError

impl Display for WebError

impl Display for BadNamever

impl Display for Interval

impl Display for BadMessage

impl Display for ExpectedKeyword

impl Display for MetadataItemError

impl Display for InvalidOrNullGitObjectId

impl Display for WorkerFidelity

impl Display for Info

impl Display for IpAddr

impl Display for IpNet

impl Display for Void

impl Display for tag2upload_service_manager::prelude::fs::TryLockError

impl Display for AsciiChar

impl Display for Infallible

impl Display for FromBytesWithNulError

impl Display for SocketAddr

impl Display for core::slice::GetDisjointMutError

impl Display for VarError

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

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

impl Display for ParseAlphabetError

impl Display for base64::decode::DecodeError

impl Display for DecodeSliceError

impl Display for EncodeSliceError

impl Display for Tz

impl Display for RoundingError

impl Display for chrono::weekday::Weekday

impl Display for ContextKind

impl Display for ContextValue

impl Display for clap_builder::error::kind::ErrorKind

impl Display for MatchesError

impl Display for ColorChoice

impl Display for cookie::parse::ParseError

impl Display for SameSite

impl Display for crossbeam_channel::err::RecvTimeoutError

impl Display for crossbeam_channel::err::TryRecvError

impl Display for DecodeKind

impl Display for BinaryError

impl Display for Actual

impl Display for figment::error::Kind

impl Display for Source

impl Display for globset::ErrorKind

impl Display for ProtoErrorKind

impl Display for MessageType

impl Display for OpCode

impl Display for ResponseCode

impl Display for DNSClass

impl Display for Property

impl Display for hickory_proto::rr::rdata::caa::Value

impl Display for Algorithm

impl Display for CertType

impl Display for SvcParamKey

impl Display for SvcParamValue

impl Display for RData

impl Display for RecordType

impl Display for hickory_proto::serialize::binary::decoder::DecodeError

impl Display for Protocol

impl Display for ResolveErrorKind

impl Display for httparse::Error

impl Display for humantime::date::Error

impl Display for humantime::duration::Error

impl Display for GetTimezoneError

Trait Display