Trait frame_support::dispatch::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)");

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 frame_support::dispatch::fmt::DisplayCopy item path

§Internationalization

§Examples

Required Methods§

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

§Errors

§Examples

Implementors§

impl Display for arbitrary::error::Error

impl Display for ParseAlphabetError

impl Display for DecodeError

impl Display for DecodeSliceError

impl Display for EncodeSliceError

impl Display for bincode::error::ErrorKind

impl Display for bip39::error::ErrorKind

impl Display for MnemonicType

impl Display for bs58::alphabet::Error

impl Display for bs58::decode::Error

impl Display for bs58::encode::Error

impl Display for byte_slice_cast::Error

impl Display for const_oid::error::Error

impl Display for cpp_demangle::error::Error

impl Display for Reloc

impl Display for DataValue

impl Display for DataValueCastFailure

impl Display for AtomicRmwOp

impl Display for FloatCC

impl Display for IntCC

impl Display for AnyEntity

impl Display for ArgumentPurpose

impl Display for UserFuncName

impl Display for GlobalValueData

impl Display for Opcode

impl Display for KnownSymbol

impl Display for LibCall

impl Display for ProgramPoint

impl Display for StackSlotKind

impl Display for TrapCode

impl Display for CallConv

impl Display for LookupError

impl Display for RegisterMappingError

impl Display for AluRmROpcode

impl Display for AluRmiROpcode

impl Display for CC

impl Display for ExtMode

impl Display for ShiftKind

impl Display for SseOpcode

impl Display for UnaryRmROpcode

impl Display for Avx512Opcode

impl Display for AvxOpcode

impl Display for UnaryRmRVexOpcode

impl Display for CodegenError

impl Display for LibcallCallConv

impl Display for OptLevel

impl Display for ProbestackStrategy

impl Display for SetError

impl Display for TlsModel

impl Display for Pass

impl Display for ed25519_zebra::error::Error

impl Display for gimli::read::Error

impl Display for gimli::read::Error

impl Display for ConvertError

impl Display for gimli::write::Error

impl Display for hex::error::FromHexError

impl Display for humantime::date::Error

impl Display for humantime::duration::Error

impl Display for leb128::read::Error

impl Display for log::Level

impl Display for log::LevelFilter

impl Display for memfd::errors::Error

impl Display for num_format::error_kind::ErrorKind

impl Display for parity_wasm::elements::Error

impl Display for Instruction

impl Display for ValueType

impl Display for BernoulliError

impl Display for WeightedError

impl Display for OperandConstraint

impl Display for RegAllocError

impl Display for regex::error::Error

impl Display for StartError

Trait frame_support::dispatch::fmt::Display