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.

§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 PublicInputError

impl Display for HashChainError

impl Display for ProgramHashError

impl Display for BuiltinName

impl Display for MathError

impl Display for ProgramError

impl Display for LayoutName

impl Display for MaybeRelocatable

impl Display for CairoPieValidationError

impl Display for CairoRunError

impl Display for ExecScopeError

impl Display for HintError

impl Display for InsufficientAllocatedCellsError

impl Display for MemoryError

impl Display for RunnerError

impl Display for TraceError

impl Display for VirtualMachineError

impl Display for Infallible

impl Display for RecvTimeoutError

impl Display for TryRecvError

impl Display for AsciiChar

impl Display for IpAddr

impl Display for SocketAddr

impl Display for VarError

impl Display for ErrorKind

impl Display for SerializationError

impl Display for DecodeError

impl Display for EncodeError

impl Display for FromHexError

impl Display for lambdaworks_crypto::merkle_tree::merkle::Error

impl Display for FFTError

impl Display for MSMError

impl Display for InterpolateError

impl Display for BernoulliError

impl Display for WeightedError

impl Display for rust_decimal::error::Error

impl Display for Value

impl Display for RecoverError

impl Display for SignError

impl Display for VerifyError

impl Display for FromByteSliceError

impl Display for starknet_ff::from_str_error::FromStrError

impl Display for CompressionMethod

impl Display for ZipError

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 EncodeTraceError

impl Display for String

impl Display for Felt

impl Display for Relocatable

impl Display for VmException

impl Display for Memory

impl Display for MemorySegmentManager

impl Display for cairo_vm::with_std::alloc::AllocError

impl Display for LayoutError

impl Display for BorrowError

Trait Display