narui::re_export::smallvec::alloc::fmt

Trait Display

1.36.0 · 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, }),
);

Dyn Compatibility§

This trait is dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Display

Trait Display Copy item path

§Completeness and parseability

§Internationalization

§Examples

Required Methods§

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

§Errors

§Examples

Dyn Compatibility§

Implementors§

impl Display for !

impl Display for AccessCheckError

impl Display for std::thread::local::AccessError

impl Display for vulkano::sync::future::AccessError

impl Display for AcquireError

impl Display for AddrParseError

impl Display for nix::sys::socket::addr::alg::AlgAddr

impl Display for nix::sys::socket::addr::alg::AlgAddr

impl Display for AllocError

impl Display for Argument

impl Display for Arguments<'_>

impl Display for AsciiChar

impl Display for Attribute<'_>

impl Display for AutoCommandBufferBuilderContextError

impl Display for Backtrace

impl Display for BadIcon

impl Display for BeginError

impl Display for BeginQueryError

impl Display for BeginRenderPassError

impl Display for BernoulliError

impl Display for BlitImageError

impl Display for BorderRadii

impl Display for BorrowError

impl Display for BorrowMutError

impl Display for BrushError

impl Display for BufferCreationError

impl Display for BufferViewCreationError

impl Display for BuildError

impl Display for ByteStr

impl Display for ByteString

impl Display for CacheWriteErr

impl Display for CapabilitiesError

impl Display for CharTryFromError

impl Display for CheckBeginQueryError

impl Display for CheckBlitImageError

impl Display for CheckClearColorImageError

impl Display for CheckClearDepthStencilImageError

impl Display for CheckColorError

impl Display for CheckCopyBufferError

impl Display for CheckCopyBufferImageError

impl Display for CheckCopyImageError

impl Display for CheckCopyQueryPoolResultsError

impl Display for CheckDescriptorSetsValidityError

impl Display for CheckDispatchError

impl Display for CheckDynamicStateValidityError

impl Display for CheckEndQueryError

impl Display for CheckFillBufferError

impl Display for CheckIndexBufferError

impl Display for CheckIndirectBufferError

impl Display for CheckPipelineError

impl Display for CheckPushConstantsValidityError

impl Display for CheckResetQueryPoolError

impl Display for CheckUpdateBufferError

impl Display for CheckVertexBufferError

impl Display for CheckWriteTimestampError

impl Display for CheckedCastError

impl Display for ClearColorImageError

impl Display for ClockId

impl Display for CollectionAllocErr

impl Display for CommandBufferExecError

impl Display for CommandPoolTrimError

impl Display for ComputePipelineCreationError

impl Display for ConformanceVersion

impl Display for ConnectError

impl Display for CopyBufferError

impl Display for CopyBufferImageError

impl Display for CopyImageError

impl Display for CopyQueryPoolResultsError

impl Display for CreationError

Trait Display