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,
)");

Debug

Trait Debug Copy item path

§Stability

§Examples

Required Methods§

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

§Errors

§Examples

Implementors§

impl Debug for AssignmentOperator

impl Debug for ArithmeticOperator

impl Debug for BinaryOperator

impl Debug for BitwiseOperator

impl Debug for LogicalOperator

impl Debug for ApplyOperation

impl Debug for ComparisonOperator

impl Debug for DatexExpression

impl Debug for Slot

impl Debug for TypeExpression

impl Debug for VariableKind

impl Debug for datex_core::ast::error::error::ErrorKind

impl Debug for SpanOrToken

impl Debug for datex_core::ast::error::pattern::Pattern

impl Debug for datex_core::ast::lexer::Token

impl Debug for ArithmeticUnaryOperator

impl Debug for BitwiseUnaryOperator

impl Debug for LogicalUnaryOperator

impl Debug for ReferenceUnaryOperator

impl Debug for UnaryOperator

impl Debug for StaticValueOrDXB

impl Debug for VariableModel

impl Debug for VariableRepresentation

impl Debug for CompilerError

impl Debug for CryptoError

impl Debug for Formatting

impl Debug for ScopeType

impl Debug for DIFApplyError

impl Debug for DIFCreatePointerError

impl Debug for DIFObserveError

impl Debug for DIFResolveReferenceError

impl Debug for DIFUpdateError

impl Debug for DIFTypeRepresentation

impl Debug for DIFValueRepresentation

impl Debug for DIFTypeContainer

impl Debug for DIFTypeDefinition

impl Debug for DIFProperty

impl Debug for DIFUpdateData

impl Debug for DIFValueContainer

impl Debug for HeaderParsingError

impl Debug for IncomingSection

impl Debug for InstructionCode

impl Debug for datex_core::global::protocol_structures::block_header::BlockType

impl Debug for UserAgent

impl Debug for Instruction

impl Debug for TypeInstruction

impl Debug for EncryptionType

impl Debug for ReceiverType

impl Debug for Receivers

impl Debug for SignatureType

impl Debug for InternalSlot

impl Debug for TypeSpaceInstructionCode

impl Debug for CoreLibPointerId

impl Debug for ComHubError

impl Debug for InterfacePriority

impl Debug for datex_core::network::com_hub::Response

impl Debug for ResponseError

impl Debug for ResponseResolutionStrategy

impl Debug for ResponseTimeout

impl Debug for SocketEndpointRegistrationError

impl Debug for NetworkTraceHopDirection

impl Debug for ComInterfaceError

impl Debug for ComInterfaceState

impl Debug for InterfaceDirection

impl Debug for ReconnectionConfig

impl Debug for SocketState

impl Debug for BaseInterfaceError

impl Debug for HTTPError

impl Debug for SerialError

impl Debug for TCPError

impl Debug for MediaKind

Trait Debug