Trait alloc::fmt::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)");
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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, }));
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Implementors§

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impl Display for AsciiChar

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impl Display for Infallible

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impl Display for IpAddr

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impl Display for SocketAddr

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impl Display for bool

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impl Display for char

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impl Display for f32

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impl Display for f64

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impl Display for i8

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impl Display for i16

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impl Display for i32

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impl Display for i64

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impl Display for i128

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impl Display for isize

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impl Display for !

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impl Display for str

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impl Display for u8

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impl Display for u16

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impl Display for u32

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impl Display for u64

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impl Display for u128

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impl Display for usize

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impl Display for AllocError

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impl Display for LayoutError

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impl Display for UnorderedKeyError

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impl Display for TryReserveError

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impl Display for FromVecWithNulError

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impl Display for IntoStringError

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impl Display for NulError

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impl Display for ParseBoolError

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impl Display for Utf8Error

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impl Display for FromUtf8Error

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impl Display for FromUtf16Error

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impl Display for String

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impl Display for TryFromSliceError

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impl Display for core::ascii::EscapeDefault

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impl Display for BorrowError

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impl Display for BorrowMutError

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impl Display for CharTryFromError

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impl Display for ParseCharError

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impl Display for DecodeUtf16Error

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impl Display for core::char::EscapeDebug

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impl Display for core::char::EscapeDefault

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impl Display for core::char::EscapeUnicode

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impl Display for ToLowercase

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impl Display for ToUppercase

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impl Display for TryFromCharError

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impl Display for FromBytesUntilNulError

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impl Display for FromBytesWithNulError

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impl Display for Ipv4Addr

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impl Display for Ipv6Addr

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

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impl Display for AddrParseError

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impl Display for SocketAddrV4

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impl Display for SocketAddrV6

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impl Display for ParseFloatError

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impl Display for ParseIntError

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impl Display for TryFromIntError

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impl Display for Location<'_>

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impl Display for PanicInfo<'_>

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impl Display for PanicMessage<'_>

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impl Display for TryFromFloatSecsError

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impl Display for Arguments<'_>

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impl Display for Error

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

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impl<'a> Display for alloc::str::EscapeDebug<'a>

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impl<'a> Display for alloc::str::EscapeDefault<'a>

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impl<'a> Display for alloc::str::EscapeUnicode<'a>

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impl<'a, K: Debug + Ord, V: Debug, A: Allocator + Clone> Display for OccupiedError<'a, K, V, A>

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

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

1.33.0 · source§

impl<Ptr> Display for Pin<Ptr>
where Ptr: Display,

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impl<T> Display for &T
where T: Display + ?Sized,

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impl<T> Display for &mut T
where T: Display + ?Sized,

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impl<T> Display for Ref<'_, T>
where T: Display + ?Sized,

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impl<T> Display for RefMut<'_, T>
where T: Display + ?Sized,

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impl<T> Display for NonZero<T>

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impl<T> Display for Saturating<T>
where T: Display,

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impl<T> Display for Wrapping<T>
where T: Display,

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impl<T: Display + ?Sized, A: Allocator> Display for Box<T, A>

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impl<T: ?Sized + Display> Display for ThinBox<T>

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impl<T: ?Sized + Display, A: Allocator> Display for Rc<T, A>

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impl<T: ?Sized + Display, A: Allocator> Display for Arc<T, A>

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impl<const N: usize> Display for GetManyMutError<N>