makepad_draw::shader::std::smallvec::alloc::fmt

Trait Debug

1.36.0 · 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 };

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 DebugCopy item path

§Stability

§Examples

Required Methods§

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

§Errors

§Examples

Implementors§

impl Debug for Animate

impl Debug for ApplyFrom

impl Debug for Area

impl Debug for AudioDeviceType

impl Debug for CxOsOp

impl Debug for CxPassParent

impl Debug for DigitDevice

impl Debug for DragItem

impl Debug for DragResponse

impl Debug for DragState

impl Debug for Ease

impl Debug for Event

impl Debug for Hit

impl Debug for HoverState

impl Debug for HttpMethod

impl Debug for KeyCode

impl Debug for LiveFieldKind

impl Debug for LivePropType

impl Debug for LiveValue

impl Debug for LogLevel

impl Debug for MacosMenu

impl Debug for MidiEvent

impl Debug for MidiPortType

impl Debug for MouseCursor

impl Debug for NetworkResponse

impl Debug for OsType

impl Debug for Play

impl Debug for ShaderTy

impl Debug for TextureFormat

impl Debug for TextureSize

impl Debug for TextureUpdated

impl Debug for Vec2Index

impl Debug for VideoPixelFormat

impl Debug for VirtualKeyboardEvent

impl Debug for WebSocketMessage

impl Debug for WindowDragQueryResponse

impl Debug for TouchState

impl Debug for VideoSource

impl Debug for HtmlNode

impl Debug for PathCommand

impl Debug for DrawShaderFieldKind

impl Debug for LiveBinOp

impl Debug for LiveScopeTarget

impl Debug for LiveToken

impl Debug for LiveUnOp

impl Debug for LiveNodeFromCborError

impl Debug for Delim

impl Debug for FullToken

impl Debug for State

impl Debug for DeJsonTok

impl Debug for DeRonTok

impl Debug for JsonValue

impl Debug for BinOp

impl Debug for ClosureDefKind

impl Debug for ExprKind

impl Debug for FnSelfKind

impl Debug for HiddenArgKind

impl Debug for Lit

impl Debug for ScopeSymKind

impl Debug for Stmt

impl Debug for TyExprKind

impl Debug for TyLit

impl Debug for UnOp

impl Debug for Val

impl Debug for VarKind

impl Debug for VarResolve

impl Debug for ShaderParserDep

impl Debug for LiveNodeFindResult

impl Debug for NavItem

impl Debug for NavOrder

impl Debug for NavRole

impl Debug for EventFlow

Trait Debug