Trait bevy_internal::utils::smallvec::alloc::fmt::Debug

1.0.0 · source ·

pub trait Debug {
    // Required method
    fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>;
}

Expand description

? formatting.

Debug should format the output in a programmer-facing, debugging context.

Generally speaking, you should just derive a Debug implementation.

When used with the alternate format specifier #?, the output is pretty-printed.

For more information on formatters, see the module-level documentation.

This trait can be used with #[derive] if all fields implement Debug. When derived for structs, it will use the name of the struct, then {, then a comma-separated list of each field’s name and Debug value, then }. For enums, it will use the name of the variant and, if applicable, (, then the Debug values of the fields, then ).

Stability

Derived Debug formats are not stable, and so may change with future Rust versions. Additionally, Debug implementations of types provided by the standard library (std, core, alloc, etc.) are not stable, and may also change with future Rust versions.

Examples

Deriving an implementation:

#[derive(Debug)]
struct Point {
    x: i32,
    y: i32,
}

let origin = Point { x: 0, y: 0 };

assert_eq!(format!("The origin is: {origin:?}"), "The origin is: Point { x: 0, y: 0 }");

Manually implementing:

use std::fmt;

struct Point {
    x: i32,
    y: i32,
}

impl fmt::Debug for Point {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("Point")
         .field("x", &self.x)
         .field("y", &self.y)
         .finish()
    }
}

let origin = Point { x: 0, y: 0 };

assert_eq!(format!("The origin is: {origin:?}"), "The origin is: Point { x: 0, y: 0 }");

There are a number of helper methods on the Formatter struct to help you with manual implementations, such as debug_struct.

Types that do not wish to use the standard suite of debug representations provided by the Formatter trait (debug_struct, debug_tuple, debug_list, debug_set, debug_map) can do something totally custom by manually writing an arbitrary representation to the Formatter.

impl fmt::Debug for Point {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "Point [{} {}]", self.x, self.y)
    }
}

Debug implementations using either derive or the debug builder API on Formatter support pretty-printing using the alternate flag: {:#?}.

Pretty-printing with #?:

#[derive(Debug)]
struct Point {
    x: i32,
    y: i32,
}

let origin = Point { x: 0, y: 0 };

assert_eq!(format!("The origin is: {origin:#?}"),
"The origin is: Point {
    x: 0,
    y: 0,
}");

Required Methods§

source

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

Formats the value using the given formatter.

Examples

use std::fmt;

struct Position {
    longitude: f32,
    latitude: f32,
}

impl fmt::Debug for Position {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_tuple("")
         .field(&self.longitude)
         .field(&self.latitude)
         .finish()
    }
}

let position = Position { longitude: 1.987, latitude: 2.983 };
assert_eq!(format!("{position:?}"), "(1.987, 2.983)");

assert_eq!(format!("{position:#?}"), "(
    1.987,
    2.983,
)");

Trait bevy_internal::utils::smallvec::alloc::fmt::Debug

Required Methods§

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

Trait Implementations§

impl ToValue for dyn Debug

fn to_value(&self) -> Value<'_>

Implementors§

impl Debug for GlyphImageFormat

impl Debug for OutlineCurve

impl Debug for AhoCorasickKind

impl Debug for aho_corasick::packed::api::MatchKind

impl Debug for aho_corasick::util::error::MatchErrorKind

impl Debug for Candidate

impl Debug for aho_corasick::util::search::Anchored

impl Debug for aho_corasick::util::search::MatchKind

impl Debug for aho_corasick::util::search::StartKind

impl Debug for ChmapPosition

impl Debug for ChmapType

impl Debug for ElemIface

impl Debug for ElemType

impl Debug for alsa::Direction

impl Debug for Round

impl Debug for ValueOr

impl Debug for SelemChannelId

impl Debug for alsa::pcm::Access

impl Debug for AudioTstampType

impl Debug for alsa::pcm::Format

impl Debug for alsa::pcm::State

impl Debug for TstampType

impl Debug for alsa::seq::EventType

impl Debug for LoadingError

impl Debug for async_broadcast::RecvError

impl Debug for async_broadcast::TryRecvError

impl Debug for async_channel::TryRecvError

impl Debug for ParseAlphabetError

impl Debug for base64::decode::DecodeError

impl Debug for DecodeSliceError

impl Debug for EncodeSliceError

impl Debug for DecodePaddingMode

impl Debug for CheckedCastError

impl Debug for PodCastError

impl Debug for BigEndian

impl Debug for LittleEndian

impl Debug for calloop::error::Error

impl Debug for PostAction

impl Debug for TimeoutAction

impl Debug for calloop::sys::Mode

impl Debug for LabelStyle

impl Debug for Severity

impl Debug for codespan_reporting::files::Error

impl Debug for DisplayStyle

impl Debug for PopError

impl Debug for FmtKind

impl Debug for NumberFmt

impl Debug for BufferSize

impl Debug for SupportedBufferSize

impl Debug for BuildStreamError

impl Debug for DefaultStreamConfigError

impl Debug for DeviceNameError

impl Debug for DevicesError

impl Debug for PauseStreamError

impl Debug for PlayStreamError

impl Debug for cpal::error::StreamError

impl Debug for SupportedStreamConfigsError

impl Debug for HostId

impl Debug for SampleFormat

impl Debug for crossbeam_channel::err::RecvTimeoutError

impl Debug for crossbeam_channel::err::TryRecvError

impl Debug for cursor_icon::CursorIcon

impl Debug for BitOrder

impl Debug for DecodeKind

impl Debug for DlError

impl Debug for DecompressionError

impl Debug for FlushCompress

impl Debug for FlushDecompress

impl Debug for flate2::mem::Status

impl Debug for gilrs::ev::Axis

impl Debug for AxisOrBtn

impl Debug for gilrs::ev::Button

impl Debug for gilrs::ev::EventType