Trait kernel::fmt::Debug

1.0.0 · source ·

pub(crate) 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 };

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

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::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 kernel::fmt::DebugCopy item path

§Stability

§Examples

Required Methods§

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

§Errors

§Examples

Implementors§

impl Debug for abi::bbqueue_ipc::Error

impl Debug for KernelMsg

impl Debug for KernelResponseBody

impl Debug for UserRequestBody

impl Debug for SerialError

impl Debug for SerialRequest

impl Debug for SerialResponse

impl Debug for byteorder::BigEndian

impl Debug for byteorder::LittleEndian

impl Debug for DecoderState

impl Debug for TryDequeueError

impl Debug for Mapping

impl Debug for StrokeAlignment

impl Debug for embedded_graphics::text::Alignment

impl Debug for Baseline

impl Debug for LineHeight

impl Debug for AnchorPoint

impl Debug for BinaryColor

impl Debug for embedded_graphics_core::pixelcolor::raw::BigEndian

impl Debug for embedded_graphics_core::pixelcolor::raw::LittleEndian

impl Debug for embedded_hal::digital::ErrorKind

impl Debug for PinState

impl Debug for embedded_hal::i2c::ErrorKind

impl Debug for NoAcknowledgeSource

impl Debug for embedded_hal::pwm::ErrorKind

impl Debug for embedded_hal::serial::ErrorKind

impl Debug for embedded_hal::spi::ErrorKind

impl Debug for Phase

impl Debug for Polarity

impl Debug for embedded_io::ErrorKind

impl Debug for embedded_io::SeekFrom

impl Debug for BumpError

impl Debug for EntryKind

impl Debug for forth3::Error

impl Debug for forth3::Mode

impl Debug for FillError

impl Debug for StrLiteralError

impl Debug for OutputError

impl Debug for StackError

impl Debug for PollNext

impl Debug for LineError

impl Debug for RingLineError

impl Debug for input_mgr::Source

impl Debug for TryStealError

impl Debug for TimerError

impl Debug for TryAcquireError

impl Debug for PollWaitError

impl Debug for WaitError

impl Debug for PrefilterConfig

impl Debug for InitError

impl Debug for mycelium_util::io::SeekFrom

impl Debug for mycelium_util::io::error::ErrorKind

impl Debug for FloatErrorKind

impl Debug for postcard::error::Error

impl Debug for SdmTy

impl Debug for Varint

impl Debug for Always

impl Debug for DecodeError

impl Debug for EncodeError

impl Debug for SerializeLevel

impl Debug for Variant

impl Debug for Version

impl Debug for DequeueError

impl Debug for ReusableError

impl Debug for PollStyle

impl Debug for Productive

impl Debug for MessageKind

impl Debug for OneshotRequestError

impl Debug for kernel::registry::RegistrationError

impl Debug for ReplyError

impl Debug for kernel::registry::SendError

impl Debug for UserHandlerError

Trait kernel::fmt::Debug