Trait Display

1.0.0 · Source

pub trait Display {
    // Required method
    fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>;
}

Expand description

Format trait for an empty format, {}.

Implementing this trait for a type will automatically implement the ToString trait for the type, allowing the usage of the .to_string() method. Prefer implementing the Display trait for a type, rather than ToString.

Display is similar to Debug, but Display is for user-facing output, and so cannot be derived.

For more information on formatters, see the module-level documentation.

§Completeness and parseability

Display for a type might not necessarily be a lossless or complete representation of the type. It may omit internal state, precision, or other information the type does not consider important for user-facing output, as determined by the type. As such, the output of Display might not be possible to parse, and even if it is, the result of parsing might not exactly match the original value.

However, if a type has a lossless Display implementation whose output is meant to be conveniently machine-parseable and not just meant for human consumption, then the type may wish to accept the same format in FromStr, and document that usage. Having both Display and FromStr implementations where the result of Display cannot be parsed with FromStr may surprise users.

§Internationalization

Because a type can only have one Display implementation, it is often preferable to only implement Display when there is a single most “obvious” way that values can be formatted as text. This could mean formatting according to the “invariant” culture and “undefined” locale, or it could mean that the type display is designed for a specific culture/locale, such as developer logs.

If not all values have a justifiably canonical textual format or if you want to support alternative formats not covered by the standard set of possible formatting traits, the most flexible approach is display adapters: methods like str::escape_default or Path::display which create a wrapper implementing Display to output the specific display format.

§Examples

Implementing Display on a type:

use std::fmt;

struct Point {
    x: i32,
    y: i32,
}

impl fmt::Display for Point {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "({}, {})", self.x, self.y)
    }
}

let origin = Point { x: 0, y: 0 };

assert_eq!(format!("The origin is: {origin}"), "The origin is: (0, 0)");

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::Display for Position {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "({}, {})", self.longitude, self.latitude)
    }
}

assert_eq!(
    "(1.987, 2.983)",
    format!("{}", Position { longitude: 1.987, latitude: 2.983, }),
);

Display

Trait Display Copy item path

§Completeness and parseability

§Internationalization

§Examples

Required Methods§

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

§Errors

§Examples

Implementors§

impl Display for &dyn Show

impl Display for Adt

impl Display for ArithOp

impl Display for AsmOperand

impl Display for AsmPiece

impl Display for AssocItem

impl Display for BinaryOp

impl Display for CmpOp

impl Display for Expr

impl Display for ExternItem

impl Display for FieldList

impl Display for GenericArg

impl Display for GenericParam

impl Display for capability_3p::ast::Item

impl Display for LogicOp

impl Display for NameOrNameRef

impl Display for Pat

impl Display for Stmt

impl Display for Type

impl Display for AgentCoordinateBuilderError

impl Display for BatchChoiceBuilderError

impl Display for BatchDownloadError

impl Display for BatchErrorDataBuilderError

impl Display for BatchErrorDetailsBuilderError

impl Display for BatchErrorProcessingError

impl Display for BatchErrorResponseBodyBuilderError

impl Display for BatchExecutionResultBuilderError

impl Display for BatchFileTripleBuilderError

impl Display for BatchIndex

impl Display for BatchInputCreationError

impl Display for BatchInputDataBuilderError

impl Display for BatchMessageBuilderError

impl Display for BatchMessageContentBuilderError

impl Display for BatchMetadataBuilderError

impl Display for BatchMetadataError

impl Display for BatchOutputDataBuilderError

impl Display for BatchOutputProcessingError

impl Display for BatchProcessingError

impl Display for BatchReconciliationError

impl Display for BatchRequestRecordBuilderError

impl Display for BatchResponseContentBuilderError

impl Display for BatchResponseRecordBuilderError

impl Display for BatchSuccessResponseBodyBuilderError

impl Display for BatchSuccessResponseHandlingError

impl Display for BatchTokenDetailsBuilderError

impl Display for BatchUsageBuilderError

impl Display for BatchValidationError

impl Display for BatchWorkspaceBuilderError

impl Display for BatchWorkspaceError

impl Display for CamelCaseTokenWithCommentBuilderError

impl Display for ContentParseError

impl Display for capability_3p::Edition

impl Display for capability_3p::ErrorKind

impl Display for ErrorSavingFailedBatchEntries

impl Display for FileMoveError

impl Display for HttpMethod

impl Display for InstructedLanguageModelAtCoordinateBuilderError

impl Display for JsonParseError

impl Display for capability_3p::JsonValue

impl Display for LanguageModelApiUrl

impl Display for LanguageModelBatchCreationError

impl Display for LanguageModelBatchWorkflowError

impl Display for LanguageModelType

impl Display for MockBatchClientError

impl Display for MockBatchConfigBuilderError

impl Display for MockBatchWorkspaceBuilderError

impl Display for MockLanguageModelClientBuilderError

impl Display for OpenAIClientError

impl Display for capability_3p::OpenAiClientRole

impl Display for ParseTokenDescriptionLineError

Trait Display