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.

§Completeness and parseability

Display for a type might not necessarily be a lossless or complete representation of the type. It may omit internal state, precision, or other information the type does not consider important for user-facing output, as determined by the type. As such, the output of Display might not be possible to parse, and even if it is, the result of parsing might not exactly match the original value.

However, if a type has a lossless Display implementation whose output is meant to be conveniently machine-parseable and not just meant for human consumption, then the type may wish to accept the same format in FromStr, and document that usage. Having both Display and FromStr implementations where the result of Display cannot be parsed with FromStr may surprise users.

§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, }),
);

Display

Trait Display Copy item path

§Completeness and parseability

§Internationalization

§Examples

Required Methods§

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

§Errors

§Examples

Implementors§

impl Display for AbortReason

impl Display for AddressBech32DecodeError

impl Display for AddressBech32EncodeError

impl Display for DateTimeError

impl Display for InvokeError<WasmRuntimeError>

impl Display for Level

impl Display for NonFungibleLocalId

impl Display for ParseBlsPublicKeyError

impl Display for ParseBlsSignatureError

impl Display for ParseComponentAddressError

impl Display for ParseDecimalError

impl Display for ParseEd25519PublicKeyError

impl Display for ParseEd25519SignatureError

impl Display for scrypto_test::prelude::ParseError

impl Display for ParseGlobalAddressError

impl Display for ParseHashError

impl Display for ParseI192Error

impl Display for ParseI256Error

impl Display for ParseI320Error

impl Display for ParseI384Error

impl Display for ParseI448Error

impl Display for ParseI512Error

impl Display for ParseI768Error

impl Display for ParseInternalAddressError

impl Display for ParseManifestAddressReservationError

impl Display for ParseManifestBlobRefError

impl Display for ParseManifestBucketError

impl Display for ParseManifestDecimalError

impl Display for ParseManifestExpressionError

impl Display for ParseManifestPreciseDecimalError

impl Display for ParseManifestProofError

impl Display for ParseNonFungibleGlobalIdError

impl Display for ParseNonFungibleLocalIdError

impl Display for ParseOwnError

impl Display for ParsePackageAddressError

impl Display for ParsePreciseDecimalError

impl Display for ParseReferenceError

impl Display for ParseResourceAddressError

impl Display for ParseSecp256k1PublicKeyError

impl Display for ParseSecp256k1SignatureError

impl Display for ParseU192Error

impl Display for ParseU256Error

impl Display for ParseU320Error

impl Display for ParseU384Error

impl Display for ParseU448Error

impl Display for ParseU512Error

impl Display for ParseU768Error

impl Display for ParseUtcDateTimeError

impl Display for TransactionHashBech32EncodeError

impl Display for WasmRuntimeError

impl Display for AsciiChar

impl Display for FromBytesWithNulError

impl Display for IpAddr

impl Display for SocketAddr

impl Display for proc_macro::TokenTree

impl Display for VarError

impl Display for std::fs::TryLockError

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

impl Display for bech32::Error

impl Display for Resolver

impl Display for cargo_toml::error::Error

impl Display for crossbeam_channel::err::RecvTimeoutError

impl Display for crossbeam_channel::err::TryRecvError

impl Display for FromHexError

impl Display for leb128::read::Error

impl Display for PredicateError

impl Display for proc_macro2::TokenTree

impl Display for radix_transactions::manifest::ast::ValueKind

impl Display for TokenType

impl Display for Token

Trait Display