Trait Display

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1.0.0 · Source

pub(crate) 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 tor_chanmgr::err::Error

impl Display for ConnBlockage

impl Display for ProxyError

impl Display for tor_circmgr::err::Error

impl Display for StreamIsolationBuilderError

impl Display for CfgAddrError

impl Display for CfgPathError

impl Display for RequestError

impl Display for BridgeParseError

impl Display for VanguardMode

impl Display for GuardMgrConfigError

impl Display for GuardMgrError

impl Display for PickGuardError

impl Display for Layer

impl Display for VanguardMgrError

impl Display for RelayLookupError

impl Display for tor_netdir::err::Error

impl Display for OnionDirLookupError

impl Display for HsDescError

impl Display for IntroAuthType

impl Display for IntroPointDescBuilderError

impl Display for ProtocolSupportError

impl Display for tor_netdoc::err::BuildError

impl Display for NetdocErrorKind

impl Display for Pos

impl Display for RelayFamilyId

impl Display for PolicyError

impl Display for MockNetError

impl Display for DirectoryKeyProviderError

impl Display for ClientError

impl Display for UploadError

impl Display for EstablishSessionError

impl Display for FatalError

impl Display for IntroRequestError

impl Display for IptError

impl Display for tor_hsservice::StartupError

impl Display for IptStoreError

impl Display for StateExpiryError

impl Display for IptEstablisherError

impl Display for ChooseIptError

impl Display for CreateIptError

impl Display for IptKeyRole

impl Display for LogContentError

impl Display for ReplayError

impl Display for DescUploadRetryError

impl Display for ConfigBuildError

impl Display for tor_hsservice::internal_prelude::DirClientError

impl Display for tor_hsservice::internal_prelude::ErrorKind

impl Display for ReconfigureError

impl Display for Void

impl Display for tor_hsservice::internal_prelude::fs::TryLockError

impl Display for core::ascii::ascii_char::AsciiChar

impl Display for Infallible

impl Display for FromBytesWithNulError

impl Display for IpAddr

impl Display for SocketAddr

impl Display for core::slice::GetDisjointMutError

impl Display for VarError

impl Display for RecvTimeoutError

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

impl Display for TokioTpErr

impl Display for FromHexError

impl Display for liblzma::stream::Error

impl Display for log::Level

impl Display for log::LevelFilter

impl Display for DeserializerError

impl Display for SerializerError

impl Display for serde_json::value::Value

impl Display for url::parser::ParseError

impl Display for SyntaxViolation

impl Display for rand::distr::bernoulli::BernoulliError

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

Trait Display