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

§Stability

§Examples

Required Methods§

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

§Examples

Implementors§

impl Debug for Action

impl Debug for ActionData

impl Debug for AriaCurrent

impl Debug for AutoComplete

impl Debug for Checked

impl Debug for DefaultActionVerb

impl Debug for HasPopup

impl Debug for Invalid

impl Debug for ListStyle

impl Debug for Live

impl Debug for Orientation

impl Debug for Role

impl Debug for SortDirection

impl Debug for TextAlign

impl Debug for TextDecoration

impl Debug for TextDirection

impl Debug for VerticalOffset

impl Debug for AccessibilitySystem

impl Debug for PluginsState

impl Debug for RunMode

impl Debug for StorageType

impl Debug for IdentifierError

impl Debug for QueryComponentError

impl Debug for QueryEntityError

impl Debug for QuerySingleError

impl Debug for ExecutorKind

impl Debug for LogLevel

impl Debug for bevy_internal::ecs::schedule::NodeId

impl Debug for ScheduleBuildError

impl Debug for HierarchyEvent

impl Debug for ButtonState

impl Debug for AxisSettingsError

impl Debug for ButtonSettingsError

impl Debug for GamepadConnection

impl Debug for GamepadEvent

impl Debug for Key

impl Debug for NativeKey

impl Debug for NativeKeyCode

impl Debug for MouseScrollUnit

impl Debug for GamepadAxisType

impl Debug for GamepadButtonType

impl Debug for KeyCode

impl Debug for MouseButton

impl Debug for ForceTouch

impl Debug for TouchPhase

impl Debug for EulerRot

impl Debug for InvalidDirectionError

impl Debug for TorusKind

impl Debug for WindingOrder

impl Debug for AccessErrorKind

impl Debug for DynamicVariant

impl Debug for ReflectKind

impl Debug for TypeInfo

impl Debug for VariantInfo

impl Debug for VariantType

impl Debug for bevy_internal::tasks::futures_lite::io::ErrorKind

impl Debug for SeekFrom

impl Debug for TimerMode

impl Debug for TransformSystem

impl Debug for ComputeGlobalTransformError

impl Debug for ApplicationLifetime

impl Debug for CompositeAlphaMode

impl Debug for CursorGrabMode

impl Debug for CursorIcon

impl Debug for FileDragAndDrop

impl Debug for Ime

impl Debug for MonitorSelection

impl Debug for PresentMode

impl Debug for WindowLevel

impl Debug for WindowMode

impl Debug for WindowPosition

impl Debug for WindowRef

impl Debug for WindowTheme