Trait Display

pub trait Display {
    // Required method
    fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>;
}

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

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, }),
);

Implementors

impl Display for VarError

impl Display for TimecatError

impl Display for CacheTableSize

impl Display for Color

impl Display for PieceType

impl Display for Square

impl Display for AsciiChar

impl Display for Infallible

impl Display for IpAddr

impl Display for SocketAddr

impl Display for GetManyMutError

impl Display for std::io::error::ErrorKind

impl Display for RecvTimeoutError

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

impl Display for bincode::error::ErrorKind

impl Display for binread::error::Error

impl Display for FileReadError

impl Display for HistoryError

impl Display for gloo_net::error::Error

impl Display for EventSourceError

impl Display for WebSocketError

impl Display for StorageError

impl Display for Value

impl Display for serde_urlencoded::ser::Error

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 Board

impl Display for BoardPosition

impl Display for BoardPositionBuilder

impl Display for JoinPathsError

impl Display for ParseBoolError

impl Display for ParseIntError

impl Display for PyErr

impl Display for AccessError

impl Display for BitBoard

impl Display for Move

impl Display for ValidOrNullMove

impl Display for WeightedMove

impl Display for Piece

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

impl Display for LayoutError

impl Display for AllocError

impl Display for TryFromSliceError

impl Display for core::ascii::EscapeDefault

impl Display for BorrowError

impl Display for BorrowMutError

impl Display for CharTryFromError

impl Display for ParseCharError

impl Display for DecodeUtf16Error

impl Display for core::char::EscapeDebug

impl Display for core::char::EscapeDefault

impl Display for core::char::EscapeUnicode

impl Display for ToLowercase

impl Display for ToUppercase

impl Display for TryFromCharError

impl Display for FromBytesUntilNulError

impl Display for FromBytesWithNulError

impl Display for Ipv4Addr

impl Display for Ipv6Addr

Writes an Ipv6Addr, conforming to the canonical style described by RFC 5952.

impl Display for AddrParseError

impl Display for SocketAddrV4

impl Display for SocketAddrV6

impl Display for ParseFloatError

impl Display for core::num::error::TryFromIntError

impl Display for Location<'_>

impl Display for PanicInfo<'_>

impl Display for PanicMessage<'_>

impl Display for Utf8Error

impl Display for TryFromFloatSecsError

impl Display for Backtrace

impl Display for std::ffi::os_str::Display<'_>

impl Display for WriterPanicked

impl Display for std::io::error::Error

impl Display for PanicHookInfo<'_>

impl Display for std::path::Display<'_>

impl Display for StripPrefixError

impl Display for ExitStatus

impl Display for ExitStatusError

impl Display for RecvError

impl Display for SystemTimeError

impl Display for ColoredString

impl Display for futures_channel::mpsc::SendError

impl Display for futures_channel::mpsc::TryRecvError

impl Display for Canceled

impl Display for QueryParams

The formatted query parameters ready to be used in a URL query string.

Examples

The resulting string does not contain a leading ? and is properly encoded:

use gloo_net::http::QueryParams;

let params = QueryParams::new();
params.append("a", "1");
params.append("b", "2");
assert_eq!(params.to_string(), "a=1&b=2".to_string());

params.append("key", "ab&c");
assert_eq!(params.to_string(), "a=1&b=2&key=ab%26c");

impl Display for JsError

impl Display for NotJsError

impl Display for http::error::Error

impl Display for MaxSizeReached

impl Display for HeaderName

impl Display for InvalidHeaderName

impl Display for InvalidHeaderValue

impl Display for ToStrError

impl Display for InvalidMethod

impl Display for Method

impl Display for InvalidStatusCode

impl Display for StatusCode

Formats the status code, including the canonical reason.

Example

assert_eq!(format!("{}", StatusCode::OK), "200 OK");

impl Display for Authority

impl Display for PathAndQuery

impl Display for Scheme

impl Display for InvalidUri

impl Display for InvalidUriParts

impl Display for Uri

impl Display for BigInt

impl Display for Boolean

impl Display for JsString

impl Display for js_sys::Number

impl Display for js_sys::TryFromIntError

impl Display for DowncastError<'_, '_>

impl Display for DowncastIntoError<'_>

impl Display for PyBackedStr

impl Display for PyBorrowError

impl Display for PyBorrowMutError

impl Display for serde_wasm_bindgen::error::Error

impl Display for serde::de::value::Error

impl Display for serde_json::error::Error

impl Display for serde_json::number::Number

impl Display for Arguments<'_>

impl Display for timecat::fmt::Error

impl Display for dyn Expected + '_

impl<'a> Display for Unexpected<'a>

impl<'a> Display for EscapeAscii<'a>

impl<'a> Display for core::str::iter::EscapeDebug<'a>

impl<'a> Display for core::str::iter::EscapeDefault<'a>

impl<'a> Display for core::str::iter::EscapeUnicode<'a>

impl<'a> Display for PercentEncode<'a>

impl<'a, I> Display for Format<'a, I>

where I: Iterator, <I as Iterator>::Item: Display,

impl<'a, K, V> Display for std::collections::hash::map::OccupiedError<'a, K, V>

where K: Debug, V: Debug,

impl<'a, K, V, A> Display for alloc::collections::btree::map::entry::OccupiedError<'a, K, V, A>

where K: Debug + Ord, V: Debug, A: Allocator + Clone,

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,

impl<F> Display for FromFn<F>

where F: Fn(&mut Formatter<'_>) -> Result<(), Error>,

impl<I> Display for ExactlyOneError<I>

where I: Iterator,

impl<I, F> Display for FormatWith<'_, I, F>

where I: Iterator, F: FnMut(<I as Iterator>::Item, &mut dyn FnMut(&dyn Display) -> Result<(), Error>) -> Result<(), Error>,

impl<L, R> Display for Either<L, R>

where L: Display, R: Display,

impl<Ptr> Display for Pin<Ptr>

where Ptr: Display,

impl<T> Display for SendTimeoutError<T>

impl<T> Display for std::sync::mpsc::TrySendError<T>

impl<T> Display for TryLockError<T>

impl<T> Display for &T

where T: Display + ?Sized,

impl<T> Display for &mut T

where T: Display + ?Sized,

impl<T> Display for Bound<'_, T>

impl<T> Display for Py<T>

where T: PyTypeInfo,

impl<T> Display for Wrapping<T>

where T: Display,

impl<T> Display for ThinBox<T>

where T: Display + ?Sized,

impl<T> Display for Ref<'_, T>

where T: Display + ?Sized,

impl<T> Display for RefMut<'_, T>

where T: Display + ?Sized,

impl<T> Display for NonZero<T>

where T: ZeroablePrimitive + Display,

impl<T> Display for Saturating<T>

where T: Display,

impl<T> Display for std::sync::mpsc::SendError<T>

impl<T> Display for MappedMutexGuard<'_, T>

where T: Display + ?Sized,

impl<T> Display for MutexGuard<'_, T>

where T: Display + ?Sized,

impl<T> Display for MappedRwLockReadGuard<'_, T>

where T: Display + ?Sized,

impl<T> Display for MappedRwLockWriteGuard<'_, T>

where T: Display + ?Sized,

impl<T> Display for RwLockReadGuard<'_, T>

where T: Display + ?Sized,

impl<T> Display for RwLockWriteGuard<'_, T>

where T: Display + ?Sized,

impl<T> Display for PoisonError<T>

impl<T> Display for ReentrantLockGuard<'_, T>

where T: Display + ?Sized,

impl<T> Display for CapacityError<T>

impl<T> Display for futures_channel::mpsc::TrySendError<T>

impl<T> Display for Port<T>

impl<T, A> Display for Arc<T, A>

where T: Display + ?Sized, A: Allocator,

impl<T, A> Display for Box<T, A>

where T: Display + ?Sized, A: Allocator,

impl<T, A> Display for Rc<T, A>

where T: Display + ?Sized, A: Allocator,

impl<T, A> Display for UniqueRc<T, A>

where T: Display + ?Sized, A: Allocator,

impl<T: ChessEngine> Display for UCIOption<T>

impl<T: Display, const N: usize> Display for MathVec<T, N>

impl<W> Display for IntoInnerError<W>

impl<const CAP: usize> Display for ArrayString<CAP>