# Trait core::fmt::Debug [−] [src]

    pub trait Debug {
        fn fmt(&self, &mut Formatter) -> Result;
    }

Format trait for the `?` character.

`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]`.

# Examples

Deriving an implementation:

fn main() { #[derive(Debug)] struct Point { x: i32, y: i32, } let origin = Point { x: 0, y: 0 }; println!("The origin is: {:?}", origin); }

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

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

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

Manually implementing:

fn main() { 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); }

    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);

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 `#?`:

fn main() { #[derive(Debug)] struct Point { x: i32, y: i32, } let origin = Point { x: 0, y: 0 }; println!("The origin is: {:#?}", origin); }

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

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

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

This outputs:

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

## Required Methods

### `fn fmt(&self, &mut Formatter) -> Result`

Formats the value using the given formatter.

## Implementors

- `impl<T: Debug> Debug for Wrapping<T>`
- `impl Debug for FpCategory`
- `impl Debug for ParseIntError`
- `impl<T: Debug + Zeroable> Debug for NonZero<T>`
- `impl<Ret> Debug for fn() -> Ret`
- `impl<Ret> Debug for extern "C" fn() -> Ret`
- `impl<Ret> Debug for unsafe fn() -> Ret`
- `impl<Ret> Debug for unsafe extern "C" fn() -> Ret`
- `impl<Ret, A> Debug for fn(A) -> Ret`
- `impl<Ret, A> Debug for extern "C" fn(A) -> Ret`
- `impl<Ret, A> Debug for unsafe fn(A) -> Ret`
- `impl<Ret, A> Debug for unsafe extern "C" fn(A) -> Ret`
- `impl<Ret, A, B> Debug for fn(A, B) -> Ret`
- `impl<Ret, A, B> Debug for extern "C" fn(A, B) -> Ret`
- `impl<Ret, A, B> Debug for unsafe fn(A, B) -> Ret`
- `impl<Ret, A, B> Debug for unsafe extern "C" fn(A, B) -> Ret`
- `impl<Ret, A, B, C> Debug for fn(A, B, C) -> Ret`
- `impl<Ret, A, B, C> Debug for extern "C" fn(A, B, C) -> Ret`
- `impl<Ret, A, B, C> Debug for unsafe fn(A, B, C) -> Ret`
- `impl<Ret, A, B, C> Debug for unsafe extern "C" fn(A, B, C) -> Ret`
- `impl<Ret, A, B, C, D> Debug for fn(A, B, C, D) -> Ret`
- `impl<Ret, A, B, C, D> Debug for extern "C" fn(A, B, C, D) -> Ret`
- `impl<Ret, A, B, C, D> Debug for unsafe fn(A, B, C, D) -> Ret`
- `impl<Ret, A, B, C, D> Debug for unsafe extern "C" fn(A, B, C, D) -> Ret`
- `impl<Ret, A, B, C, D, E> Debug for fn(A, B, C, D, E) -> Ret`
- `impl<Ret, A, B, C, D, E> Debug for extern "C" fn(A, B, C, D, E) -> Ret`
- `impl<Ret, A, B, C, D, E> Debug for unsafe fn(A, B, C, D, E) -> Ret`
- `impl<Ret, A, B, C, D, E> Debug for unsafe extern "C" fn(A, B, C, D, E) -> Ret`
- `impl<Ret, A, B, C, D, E, F> Debug for fn(A, B, C, D, E, F) -> Ret`
- `impl<Ret, A, B, C, D, E, F> Debug for extern "C" fn(A, B, C, D, E, F) -> Ret`
- `impl<Ret, A, B, C, D, E, F> Debug for unsafe fn(A, B, C, D, E, F) -> Ret`
- `impl<Ret, A, B, C, D, E, F> Debug for unsafe extern "C" fn(A, B, C, D, E, F) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G> Debug for fn(A, B, C, D, E, F, G) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G> Debug for extern "C" fn(A, B, C, D, E, F, G) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G> Debug for unsafe fn(A, B, C, D, E, F, G) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G> Debug for unsafe extern "C" fn(A, B, C, D, E, F, G) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H> Debug for fn(A, B, C, D, E, F, G, H) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H> Debug for extern "C" fn(A, B, C, D, E, F, G, H) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H> Debug for unsafe fn(A, B, C, D, E, F, G, H) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H> Debug for unsafe extern "C" fn(A, B, C, D, E, F, G, H) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I> Debug for fn(A, B, C, D, E, F, G, H, I) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I> Debug for extern "C" fn(A, B, C, D, E, F, G, H, I) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I> Debug for unsafe fn(A, B, C, D, E, F, G, H, I) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I> Debug for unsafe extern "C" fn(A, B, C, D, E, F, G, H, I) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I, J> Debug for fn(A, B, C, D, E, F, G, H, I, J) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I, J> Debug for extern "C" fn(A, B, C, D, E, F, G, H, I, J) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I, J> Debug for unsafe fn(A, B, C, D, E, F, G, H, I, J) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I, J> Debug for unsafe extern "C" fn(A, B, C, D, E, F, G, H, I, J) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I, J, K> Debug for fn(A, B, C, D, E, F, G, H, I, J, K) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I, J, K> Debug for extern "C" fn(A, B, C, D, E, F, G, H, I, J, K) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I, J, K> Debug for unsafe fn(A, B, C, D, E, F, G, H, I, J, K) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I, J, K> Debug for unsafe extern "C" fn(A, B, C, D, E, F, G, H, I, J, K) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I, J, K, L> Debug for fn(A, B, C, D, E, F, G, H, I, J, K, L) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I, J, K, L> Debug for extern "C" fn(A, B, C, D, E, F, G, H, I, J, K, L) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I, J, K, L> Debug for unsafe fn(A, B, C, D, E, F, G, H, I, J, K, L) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I, J, K, L> Debug for unsafe extern "C" fn(A, B, C, D, E, F, G, H, I, J, K, L) -> Ret`
- `impl Debug for RangeFull`
- `impl<Idx: Debug> Debug for Range<Idx>`
- `impl<Idx: Debug> Debug for RangeFrom<Idx>`
- `impl<Idx: Debug> Debug for RangeTo<Idx>`
- `impl Debug for Ordering`
- `impl Debug for Any`
- `impl Debug for Any + Send`
- `impl Debug for TypeId`
- `impl<T: Debug> Debug for [T; 0]`
- `impl<T: Debug> Debug for [T; 1]`
- `impl<T: Debug> Debug for [T; 2]`
- `impl<T: Debug> Debug for [T; 3]`
- `impl<T: Debug> Debug for [T; 4]`
- `impl<T: Debug> Debug for [T; 5]`
- `impl<T: Debug> Debug for [T; 6]`
- `impl<T: Debug> Debug for [T; 7]`
- `impl<T: Debug> Debug for [T; 8]`
- `impl<T: Debug> Debug for [T; 9]`
- `impl<T: Debug> Debug for [T; 10]`
- `impl<T: Debug> Debug for [T; 11]`
- `impl<T: Debug> Debug for [T; 12]`
- `impl<T: Debug> Debug for [T; 13]`
- `impl<T: Debug> Debug for [T; 14]`
- `impl<T: Debug> Debug for [T; 15]`
- `impl<T: Debug> Debug for [T; 16]`
- `impl<T: Debug> Debug for [T; 17]`
- `impl<T: Debug> Debug for [T; 18]`
- `impl<T: Debug> Debug for [T; 19]`
- `impl<T: Debug> Debug for [T; 20]`
- `impl<T: Debug> Debug for [T; 21]`
- `impl<T: Debug> Debug for [T; 22]`
- `impl<T: Debug> Debug for [T; 23]`
- `impl<T: Debug> Debug for [T; 24]`
- `impl<T: Debug> Debug for [T; 25]`
- `impl<T: Debug> Debug for [T; 26]`
- `impl<T: Debug> Debug for [T; 27]`
- `impl<T: Debug> Debug for [T; 28]`
- `impl<T: Debug> Debug for [T; 29]`
- `impl<T: Debug> Debug for [T; 30]`
- `impl<T: Debug> Debug for [T; 31]`
- `impl<T: Debug> Debug for [T; 32]`
- `impl Debug for AtomicUsize`
- `impl Debug for AtomicIsize`
- `impl Debug for AtomicBool`
- `impl<T> Debug for AtomicPtr<T>`
- `impl Debug for BorrowState`
- `impl<T: Debug> Debug for Option<T>`
- `impl<T: Debug, E: Debug> Debug for Result<T, E>`
- `impl Debug for SearchStep`
- `impl<'a, 'b> Debug for StrSearcher<'a, 'b>`
- `impl Debug for ParseBoolError`
- `impl Debug for Utf8Error`
- `impl Debug for RadixFmt<isize, Radix>`
- `impl Debug for isize`
- `impl Debug for RadixFmt<usize, Radix>`
- `impl Debug for usize`
- `impl Debug for RadixFmt<i8, Radix>`
- `impl Debug for i8`
- `impl Debug for RadixFmt<u8, Radix>`
- `impl Debug for u8`
- `impl Debug for RadixFmt<i16, Radix>`
- `impl Debug for i16`
- `impl Debug for RadixFmt<u16, Radix>`
- `impl Debug for u16`
- `impl Debug for RadixFmt<i32, Radix>`
- `impl Debug for i32`
- `impl Debug for RadixFmt<u32, Radix>`
- `impl Debug for u32`
- `impl Debug for RadixFmt<i64, Radix>`
- `impl Debug for i64`
- `impl Debug for RadixFmt<u64, Radix>`
- `impl Debug for u64`
- `impl Debug for Error`
- `impl<'a> Debug for Arguments<'a>`
- `impl<'a, T: ?Sized + Debug> Debug for &'a T`
- `impl<'a, T: ?Sized + Debug> Debug for &'a mut T`
- `impl Debug for bool`
- `impl Debug for str`
- `impl Debug for char`
- `impl Debug for f32`
- `impl Debug for f64`
- `impl<T> Debug for *const T`
- `impl<T> Debug for *mut T`
- `impl<T0: Debug, T1: Debug, T2: Debug, T3: Debug, T4: Debug, T5: Debug, T6: Debug, T7: Debug, T8: Debug, T9: Debug, T10: Debug, T11: Debug> Debug for (T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11)`
- `impl<T1: Debug, T2: Debug, T3: Debug, T4: Debug, T5: Debug, T6: Debug, T7: Debug, T8: Debug, T9: Debug, T10: Debug, T11: Debug> Debug for (T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11)`
- `impl<T2: Debug, T3: Debug, T4: Debug, T5: Debug, T6: Debug, T7: Debug, T8: Debug, T9: Debug, T10: Debug, T11: Debug> Debug for (T2, T3, T4, T5, T6, T7, T8, T9, T10, T11)`
- `impl<T3: Debug, T4: Debug, T5: Debug, T6: Debug, T7: Debug, T8: Debug, T9: Debug, T10: Debug, T11: Debug> Debug for (T3, T4, T5, T6, T7, T8, T9, T10, T11)`
- `impl<T4: Debug, T5: Debug, T6: Debug, T7: Debug, T8: Debug, T9: Debug, T10: Debug, T11: Debug> Debug for (T4, T5, T6, T7, T8, T9, T10, T11)`
- `impl<T5: Debug, T6: Debug, T7: Debug, T8: Debug, T9: Debug, T10: Debug, T11: Debug> Debug for (T5, T6, T7, T8, T9, T10, T11)`
- `impl<T6: Debug, T7: Debug, T8: Debug, T9: Debug, T10: Debug, T11: Debug> Debug for (T6, T7, T8, T9, T10, T11)`
- `impl<T7: Debug, T8: Debug, T9: Debug, T10: Debug, T11: Debug> Debug for (T7, T8, T9, T10, T11)`
- `impl<T8: Debug, T9: Debug, T10: Debug, T11: Debug> Debug for (T8, T9, T10, T11)`
- `impl<T9: Debug, T10: Debug, T11: Debug> Debug for (T9, T10, T11)`
- `impl<T10: Debug, T11: Debug> Debug for (T10, T11)`
- `impl<T11: Debug> Debug for (T11,)`
- `impl<T: Debug> Debug for [T]`
- `impl Debug for ()`
- `impl<T: ?Sized> Debug for PhantomData<T>`
- `impl<T: Copy + Debug> Debug for Cell<T>`
- `impl<T: ?Sized + Debug> Debug for RefCell<T>`
- `impl<'b, T: ?Sized + Debug> Debug for Ref<'b, T>`
- `impl<'b, T: ?Sized + Debug> Debug for RefMut<'b, T>`

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