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 ConditionalOperator

impl Display for ConfigError

impl Display for VarError

impl Display for AsciiChar

impl Display for Infallible

impl Display for IpAddr

impl Display for SocketAddr

impl Display for RecvTimeoutError

impl Display for TryRecvError

impl Display for RoundingError

impl Display for 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 Shell

impl Display for ctrlc::error::Error

impl Display for dotenvy::errors::Error

impl Display for GetTimezoneError

impl Display for nix::errno::consts::Errno

impl Display for Signal

impl Display for BernoulliError

impl Display for WeightedError

impl Display for StartError

impl Display for regex_syntax::ast::Ast

impl Display for regex_syntax::ast::ErrorKind

impl Display for regex_syntax::error::Error

impl Display for regex_syntax::hir::ErrorKind

impl Display for regex::error::Error

impl Display for Value

impl Display for ChangeTag

impl Display for StrSimError

impl Display for strum::ParseError

impl Display for Variant

impl Display for pub_just::io::ErrorKind

impl Display for Keyword

impl Display for OutputError

impl Display for SearchError

impl Display for Thunk<'_>

impl Display for TokenKind

impl Display for UnstableFeature

impl Display for bool

impl Display for char

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

impl Display for u64

impl Display for u128

impl Display for usize

impl Display for CompileError<'_>

impl Display for JoinPathsError

impl Display for Arguments<'_>

impl Display for pub_just::fmt::Error

impl Display for UnorderedKeyError

impl Display for TryReserveError

impl Display for FromVecWithNulError

impl Display for IntoStringError

impl Display for NulError

impl Display for FromUtf8Error

impl Display for FromUtf16Error

impl Display for String

Trait Display