Trait frame_support::dispatch::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 frame_support::dispatch::fmt::Debug

Stability

Examples

Required Methods§

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

Examples

Implementors§

impl Debug for Never

impl Debug for Void

impl Debug for frame_support::pallet_prelude::DispatchError

impl Debug for InvalidTransaction

impl Debug for TransactionSource

impl Debug for TransactionValidityError

impl Debug for UnknownTransaction

impl Debug for ChildInfo

impl Debug for ChildType

impl Debug for StateVersion

impl Debug for ExecuteOverweightError

impl Debug for ProcessMessageError

impl Debug for frame_support::traits::schedule::LookupError

impl Debug for BalanceStatus

impl Debug for DepositConsequence

impl Debug for ExistenceRequirement

impl Debug for DispatchClass

impl Debug for Pays

impl Debug for frame_support::dispatch::fmt::Alignment

impl Debug for TryReserveErrorKind

impl Debug for core::cmp::Ordering

impl Debug for core::convert::Infallible

impl Debug for Which

impl Debug for c_void

impl Debug for FpCategory

impl Debug for IntErrorKind

impl Debug for SearchStep

impl Debug for core::sync::atomic::Ordering

impl Debug for BacktraceStatus

impl Debug for VarError

impl Debug for SeekFrom

impl Debug for std::io::error::ErrorKind

impl Debug for Shutdown

impl Debug for IpAddr

impl Debug for Ipv6MulticastScope

impl Debug for std::net::socket_addr::SocketAddr

impl Debug for AncillaryError

impl Debug for BacktraceStyle

impl Debug for RecvTimeoutError

impl Debug for std::sync::mpsc::TryRecvError

impl Debug for _Unwind_Reason_Code

impl Debug for base16ct::error::Error

impl Debug for bincode::error::ErrorKind

impl Debug for SecondsFormat

impl Debug for Fixed

impl Debug for Numeric

impl Debug for Pad

impl Debug for ParseErrorKind

impl Debug for Month

impl Debug for RoundingError

impl Debug for Weekday

impl Debug for RuntimeMetadata

impl Debug for RuntimeMetadataDeprecated

impl Debug for StorageEntryModifier

impl Debug for StorageHasher

impl Debug for hex::error::FromHexError

impl Debug for log::Level

impl Debug for log::LevelFilter

impl Debug for Sign

impl Debug for num_format::error_kind::ErrorKind

impl Debug for Grouping

impl Debug for Locale

impl Debug for FloatErrorKind

impl Debug for pkcs8::error::Error

impl Debug for pkcs8::version::Version

impl Debug for MetaForm

impl Debug for PortableForm

impl Debug for TypeDefPrimitive

impl Debug for PathError

impl Debug for Always

impl Debug for Category

impl Debug for serde_json::value::Value

impl Debug for CollectionAllocErr