Trait 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 };

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 AddressBech32DecodeError

impl Debug for AddressBech32EncodeError

impl Debug for AlwaysVisibleGlobalNodesVersion

impl Debug for SystemExecution

impl Debug for ParseBlsPublicKeyError

impl Debug for ParseBlsSignatureError

impl Debug for ParseEd25519PublicKeyError

impl Debug for ParseEd25519SignatureError

impl Debug for ParseHashError

impl Debug for ParseSecp256k1PublicKeyError

impl Debug for ParseSecp256k1SignatureError

impl Debug for radix_common::crypto::PublicKey

impl Debug for PublicKeyHash

impl Debug for ManifestCustomExtension

impl Debug for ManifestCustomTraversal

impl Debug for ManifestCustomValue

impl Debug for ManifestCustomValueKind

impl Debug for ManifestToRustValueError

impl Debug for RustToManifestValueError

impl Debug for AllowedIds

impl Debug for LowerBound

impl Debug for ManifestAddress

impl Debug for ManifestBucketBatch

impl Debug for ManifestComponentAddress

impl Debug for ManifestExpression

impl Debug for ManifestGlobalAddress

impl Debug for ManifestNonFungibleLocalId

impl Debug for ManifestNonFungibleLocalIdValidationError

impl Debug for ManifestPackageAddress

impl Debug for ManifestProofBatch

impl Debug for ManifestResourceAddress

impl Debug for ManifestResourceConstraint

impl Debug for ParseManifestAddressReservationError

impl Debug for ParseManifestBlobRefError

impl Debug for ParseManifestBucketError

impl Debug for ParseManifestDecimalError

impl Debug for ParseManifestExpressionError

impl Debug for ParseManifestPreciseDecimalError

impl Debug for ParseManifestProofError

impl Debug for ResourceConstraintError

impl Debug for ResourceConstraintsError

impl Debug for UpperBound

impl Debug for OwnValidation

impl Debug for ReferenceValidation

impl Debug for ScryptoCustomTraversal

impl Debug for ScryptoCustomTypeKind

impl Debug for ScryptoCustomTypeKindLabel

impl Debug for ScryptoCustomTypeValidation

impl Debug for ScryptoCustomValue

impl Debug for ScryptoCustomValueKind

impl Debug for ContentValidationError

impl Debug for NonFungibleIdType

impl Debug for NonFungibleLocalId

impl Debug for ParseNonFungibleLocalIdError

impl Debug for ParseOwnError

impl Debug for ParseReferenceError

impl Debug for ParseI192Error

impl Debug for ParseI256Error

impl Debug for ParseI320Error

impl Debug for ParseI384Error

impl Debug for ParseI448Error

impl Debug for ParseI512Error

impl Debug for ParseI768Error

impl Debug for ParseU192Error

impl Debug for ParseU256Error

impl Debug for ParseU320Error

impl Debug for ParseU384Error

impl Debug for ParseU448Error

impl Debug for ParseU512Error

impl Debug for ParseU768Error

impl Debug for ParseDecimalError

impl Debug for ParsePreciseDecimalError

Trait Debug