1.0.0[−][src]Trait core::fmt::Debug

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#[lang = "debug_trait"]
pub trait Debug {
    fn fmt(&self, f: &mut Formatter) -> Result;
}

[−]

? 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 ).

Examples

Deriving an implementation:

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

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

println!("The origin is: {:?}", origin);Run

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 {
        write!(f, "Point {{ x: {}, y: {} }}", self.x, self.y)
    }
}

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

println!("The origin is: {:?}", origin);Run

This outputs:

The origin is: Point { x: 0, y: 0 }

There are a number of debug_* methods on Formatter to help you with manual implementations, such as debug_struct.

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 };

println!("The origin is: {:#?}", origin);Run

This outputs:

The origin is: Point {
    x: 0,
    y: 0
}

Required methods

`fn fmt(&self, f: &mut Formatter) -> Result`[−]

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 {
        write!(f, "({:?}, {:?})", self.longitude, self.latitude)
    }
}

assert_eq!("(1.987, 2.983)".to_owned(),
           format!("{:?}", Position { longitude: 1.987, latitude: 2.983, }));Run

1.0.0[−][src]Trait core::fmt::Debug

Examples

Required methods

fn fmt(&self, f: &mut Formatter) -> Result[−]

Examples

Implementors

impl Debug for ![src][−]

fn fmt(&self, _: &mut Formatter) -> Result[src]

impl Debug for ()[src][−]

fn fmt(&self, f: &mut Formatter) -> Result[src]

impl Debug for core::cmp::Ordering[src][−]

fn fmt(&self, f: &mut Formatter) -> Result[src]

impl Debug for Infallible[src][−]

fn fmt(&self, _: &mut Formatter) -> Result[src]

impl Debug for c_void[src][−]

fn fmt(&self, f: &mut Formatter) -> Result[src]

impl Debug for Alignment[src][−]

fn fmt(&self, f: &mut Formatter) -> Result[src]

impl Debug for FpCategory[src][−]

fn fmt(&self, f: &mut Formatter) -> Result[src]

impl Debug for IntErrorKind[src][−]

fn fmt(&self, f: &mut Formatter) -> Result[src]

impl Debug for SearchStep[src][−]

fn fmt(&self, f: &mut Formatter) -> Result[src]

impl Debug for core::sync::atomic::Ordering[src][−]

fn fmt(&self, f: &mut Formatter) -> Result[src]

impl Debug for AllocErr[src][−]

fn fmt(&self, f: &mut Formatter) -> Result[src]

impl Debug for CannotReallocInPlace[src][−]

fn fmt(&self, f: &mut Formatter) -> Result[src]

impl Debug for Excess[src][−]

fn fmt(&self, f: &mut Formatter) -> Result[src]

impl Debug for Layout[src][−]

fn fmt(&self, f: &mut Formatter) -> Result[src]

impl Debug for LayoutErr[src][−]

fn fmt(&self, f: &mut Formatter) -> Result[src]

impl Debug for TypeId[src][−]

fn fmt(&self, f: &mut Formatter) -> Result[src]

impl Debug for float64x1_t[src][−]

fn fmt(&self, f: &mut Formatter) -> Result[src]

impl Debug for float64x2_t[src][−]

fn fmt(&self, f: &mut Formatter) -> Result[src]

impl Debug for poly64x1_t[src][−]

fn fmt(&self, f: &mut Formatter) -> Result[src]

impl Debug for poly64x2_t[src][−]

fn fmt(&self, f: &mut Formatter) -> Result[src]

impl Debug for float32x2_t[src][−]

fn fmt(&self, f: &mut Formatter) -> Result[src]

impl Debug for float32x4_t[src][−]

fn fmt(&self, f: &mut Formatter) -> Result[src]

impl Debug for int16x4_t[src][−]

fn fmt(&self, f: &mut Formatter) -> Result[src]

impl Debug for int16x8_t[src][−]

fn fmt(&self, f: &mut Formatter) -> Result[src]

impl Debug for int32x2_t[src][−]

fn fmt(&self, f: &mut Formatter) -> Result[src]

impl Debug for int32x4_t[src][−]

fn fmt(&self, f: &mut Formatter) -> Result[src]

impl Debug for int64x1_t[src][−]

fn fmt(&self, f: &mut Formatter) -> Result[src]

impl Debug for int64x2_t[src][−]

fn fmt(&self, f: &mut Formatter) -> Result[src]

impl Debug for int8x16_t[src][−]

fn fmt(&self, f: &mut Formatter) -> Result[src]

impl Debug for int8x8_t[src][−]

fn fmt(&self, f: &mut Formatter) -> Result[src]

impl Debug for poly16x4_t[src][−]

fn fmt(&self, f: &mut Formatter) -> Result[src]

impl Debug for poly16x8_t[src][−]

fn fmt(&self, f: &mut Formatter) -> Result[src]

impl Debug for poly8x16_t[src][−]

fn fmt(&self, f: &mut Formatter) -> Result[src]

impl Debug for poly8x8_t[src][−]

fn fmt(&self, f: &mut Formatter) -> Result[src]

impl Debug for uint16x4_t[src][−]

fn fmt(&self, f: &mut Formatter) -> Result[src]

impl Debug for uint16x8_t[src][−]

fn fmt(&self, f: &mut Formatter) -> Result[src]

impl Debug for uint32x2_t[src][−]

fn fmt(&self, f: &mut Formatter) -> Result[src]

`fn fmt(&self, f: &mut Formatter) -> Result`[−]

`impl Debug for !`[src][−]

`fn fmt(&self, _: &mut Formatter) -> Result`[src]

`impl Debug for ()`[src][−]

`fn fmt(&self, f: &mut Formatter) -> Result`[src]

`impl Debug for core::cmp::Ordering`[src][−]

`fn fmt(&self, f: &mut Formatter) -> Result`[src]

`impl Debug for Infallible`[src][−]

`fn fmt(&self, _: &mut Formatter) -> Result`[src]

`impl Debug for c_void`[src][−]

`fn fmt(&self, f: &mut Formatter) -> Result`[src]

`impl Debug for Alignment`[src][−]

`fn fmt(&self, f: &mut Formatter) -> Result`[src]

`impl Debug for FpCategory`[src][−]

`fn fmt(&self, f: &mut Formatter) -> Result`[src]

`impl Debug for IntErrorKind`[src][−]

`fn fmt(&self, f: &mut Formatter) -> Result`[src]

`impl Debug for SearchStep`[src][−]

`fn fmt(&self, f: &mut Formatter) -> Result`[src]

`impl Debug for core::sync::atomic::Ordering`[src][−]

`fn fmt(&self, f: &mut Formatter) -> Result`[src]

`impl Debug for AllocErr`[src][−]

`fn fmt(&self, f: &mut Formatter) -> Result`[src]

`impl Debug for CannotReallocInPlace`[src][−]

`fn fmt(&self, f: &mut Formatter) -> Result`[src]

`impl Debug for Excess`[src][−]

`fn fmt(&self, f: &mut Formatter) -> Result`[src]

`impl Debug for Layout`[src][−]

`fn fmt(&self, f: &mut Formatter) -> Result`[src]

`impl Debug for LayoutErr`[src][−]

`fn fmt(&self, f: &mut Formatter) -> Result`[src]

`impl Debug for TypeId`[src][−]

`fn fmt(&self, f: &mut Formatter) -> Result`[src]

`impl Debug for float64x1_t`[src][−]

`fn fmt(&self, f: &mut Formatter) -> Result`[src]

`impl Debug for float64x2_t`[src][−]

`fn fmt(&self, f: &mut Formatter) -> Result`[src]

`impl Debug for poly64x1_t`[src][−]

`fn fmt(&self, f: &mut Formatter) -> Result`[src]

`impl Debug for poly64x2_t`[src][−]

`fn fmt(&self, f: &mut Formatter) -> Result`[src]

`impl Debug for float32x2_t`[src][−]

`fn fmt(&self, f: &mut Formatter) -> Result`[src]

`impl Debug for float32x4_t`[src][−]

`fn fmt(&self, f: &mut Formatter) -> Result`[src]

`impl Debug for int16x4_t`[src][−]

`fn fmt(&self, f: &mut Formatter) -> Result`[src]

`impl Debug for int16x8_t`[src][−]

`fn fmt(&self, f: &mut Formatter) -> Result`[src]

`impl Debug for int32x2_t`[src][−]

`fn fmt(&self, f: &mut Formatter) -> Result`[src]

`impl Debug for int32x4_t`[src][−]

`fn fmt(&self, f: &mut Formatter) -> Result`[src]

`impl Debug for int64x1_t`[src][−]

`fn fmt(&self, f: &mut Formatter) -> Result`[src]

`impl Debug for int64x2_t`[src][−]

`fn fmt(&self, f: &mut Formatter) -> Result`[src]

`impl Debug for int8x16_t`[src][−]

`fn fmt(&self, f: &mut Formatter) -> Result`[src]

`impl Debug for int8x8_t`[src][−]

`fn fmt(&self, f: &mut Formatter) -> Result`[src]

`impl Debug for poly16x4_t`[src][−]

`fn fmt(&self, f: &mut Formatter) -> Result`[src]

`impl Debug for poly16x8_t`[src][−]

`fn fmt(&self, f: &mut Formatter) -> Result`[src]

`impl Debug for poly8x16_t`[src][−]

`fn fmt(&self, f: &mut Formatter) -> Result`[src]

`impl Debug for poly8x8_t`[src][−]

`fn fmt(&self, f: &mut Formatter) -> Result`[src]

`impl Debug for uint16x4_t`[src][−]

`fn fmt(&self, f: &mut Formatter) -> Result`[src]

`impl Debug for uint16x8_t`[src][−]

`fn fmt(&self, f: &mut Formatter) -> Result`[src]

`impl Debug for uint32x2_t`[src][−]

`fn fmt(&self, f: &mut Formatter) -> Result`[src]

`impl Debug for uint32x4_t`[src][−]

`fn fmt(&self, f: &mut Formatter) -> Result`[src]

`impl Debug for uint64x1_t`[src][−]

`fn fmt(&self, f: &mut Formatter) -> Result`[src]

`impl Debug for uint64x2_t`[src][−]