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 crossbeam_channel::err::RecvTimeoutError

impl Display for crossbeam_channel::err::TryRecvError

impl Display for BernoulliError

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

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

impl Display for regex::error::Error

impl Display for StartError

impl Display for 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 BigEndian

impl Display for LittleEndian

impl Display for AsciiChar

impl Display for Infallible

impl Display for VarError

impl Display for FromBytesWithNulError

impl Display for cs431_homework::test::loom::io::ErrorKind

impl Display for IpAddr

impl Display for SocketAddr

impl Display for GetDisjointMutError

impl Display for cs431_homework::test::loom::sync::mpmc::RecvTimeoutError

impl Display for cs431_homework::test::loom::sync::mpmc::TryRecvError

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 aho_corasick::util::error::BuildError

impl Display for aho_corasick::util::error::MatchError

impl Display for aho_corasick::util::primitives::PatternIDError

impl Display for aho_corasick::util::primitives::StateIDError

impl Display for crossbeam_channel::err::RecvError

impl Display for SelectTimeoutError

impl Display for TrySelectError

impl Display for getrandom::error::Error

impl Display for Empty

impl Display for OsError

impl Display for regex::regex::bytes::Regex

impl Display for regex::regex::string::Regex

impl Display for regex_automata::dfa::onepass::BuildError

impl Display for regex_automata::hybrid::error::BuildError

impl Display for CacheError

impl Display for regex_automata::meta::error::BuildError

impl Display for regex_automata::nfa::thompson::error::BuildError

impl Display for GroupInfoError

impl Display for UnicodeWordBoundaryError

impl Display for regex_automata::util::primitives::PatternIDError

impl Display for SmallIndexError

impl Display for regex_automata::util::primitives::StateIDError

impl Display for regex_automata::util::search::MatchError

impl Display for PatternSetInsertError

impl Display for DeserializeError

impl Display for SerializeError

impl Display for regex_syntax::ast::Error

impl Display for regex_syntax::hir::Error

impl Display for Hir

impl Display for CaseFoldError

impl Display for UnicodeWordError

Trait Display

impl<'a, K, V> Display for cs431_homework::test::loom::collections::hash_map::OccupiedError<'a, K, V>
where K: Debug, V: Debug,

impl<'a, K, V, A> Display for cs431_homework::test::loom::collections::btree_map::OccupiedError<'a, K, V, A>
where K: Debug + Ord, V: Debug, A: Allocator + Clone,

impl<A, S, V> Display for ConvertError<A, S, V>
where A: Display, S: Display, V: Display,

impl<B> Display for Cow<'_, B>
where B: Display + ToOwned + ?Sized, <B as ToOwned>::Owned: Display,

impl<E> Display for Report<E>
where E: Error,