uniffi::deps::static_assertions::_core::fmt

Trait Debug

1.6.0 · 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 AnsiColor

impl Debug for Color

impl Debug for Action

impl Debug for State

impl Debug for askama::error::Error

impl Debug for DependencyKind

impl Debug for Applicability

impl Debug for DiagnosticLevel

impl Debug for CargoOpt

impl Debug for Edition

impl Debug for cargo_metadata::errors::Error

impl Debug for Message

impl Debug for Cfg

impl Debug for CfgExpr

impl Debug for cargo_platform::Platform

impl Debug for ParseErrorKind

impl Debug for ArgAction

impl Debug for ArgPredicate

impl Debug for ValueHint

impl Debug for ContextKind

impl Debug for ContextValue

impl Debug for clap_builder::error::kind::ErrorKind

impl Debug for MatchesError

impl Debug for ValueSource

impl Debug for clap_builder::util::color::ColorChoice

impl Debug for colorchoice::ColorChoice

impl Debug for IndexType

impl Debug for Container

impl Debug for Hint

impl Debug for goblin::error::Error

impl Debug for SymbolKind

impl Debug for CommandVariant

impl Debug for goblin::mach::load_command::Platform

impl Debug for StackFrameOffset

impl Debug for UnwindOperation

impl Debug for ExportAddressTableEntry

impl Debug for PrefilterConfig

impl Debug for nom::error::ErrorKind

impl Debug for VerboseErrorKind

impl Debug for Needed

impl Debug for Endianness

impl Debug for CompareResult

impl Debug for oneshot_uniffi::errors::RecvTimeoutError

impl Debug for oneshot_uniffi::errors::TryRecvError

impl Debug for plain::error::Error

impl Debug for StrCtx

impl Debug for Endian

impl Debug for scroll::error::Error

impl Debug for Op

impl Debug for Category

impl Debug for serde_json::value::Value

impl Debug for StrSimError

impl Debug for toml::ser::Error

impl Debug for toml::value::Value

impl Debug for uniffi_bindgen::bindings::kotlin::gen_kotlin::ImportRequirement

impl Debug for uniffi_bindgen::bindings::python::gen_python::ImportRequirement

impl Debug for FfiType

impl Debug for UniffiTrait

impl Debug for ErrorMetadata

impl Debug for LiteralMetadata

impl Debug for uniffi_meta::Metadata

impl Debug for Radix

impl Debug for UniffiTraitMetadata

impl Debug for ExternalKind

impl Debug for ObjectImpl

impl Debug for uniffi_meta::types::Type

impl Debug for Special

impl Debug for StringifierOrInheritOrStatic

impl Debug for StringifierOrStatic

impl Debug for FloatingPointType

impl Debug for IntegerType

impl Debug for CallbackResult

Trait Debug