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 Slot

impl Display for TypeDeclarationKind

impl Display for VariableKind

impl Display for ResolvedVariable

impl Display for CompilerError

impl Display for VariableShape

impl Display for CryptoError

impl Display for DIFApplyError

impl Display for DIFCreatePointerError

impl Display for DIFObserveError

impl Display for DIFResolveReferenceError

impl Display for DIFUpdateError

impl Display for HeaderParsingError

impl Display for InstructionCode

impl Display for AssignmentOperator

impl Display for ArithmeticOperator

impl Display for BinaryOperator

impl Display for BitwiseOperator

impl Display for LogicalOperator

impl Display for ComparisonOperator

impl Display for ArithmeticUnaryOperator

impl Display for BitwiseUnaryOperator

impl Display for LogicalUnaryOperator

impl Display for ReferenceUnaryOperator

impl Display for UnaryOperator

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

impl Display for Instruction

impl Display for RegularInstruction

impl Display for TypeInstruction

impl Display for Receivers

impl Display for InternalSlot

impl Display for TypeInstructionCode

impl Display for TypeMutabilityCode

impl Display for CoreLibPointerId

impl Display for ComHubError

impl Display for ResponseError

impl Display for NetworkTraceHopDirection

impl Display for BaseInterfaceError

impl Display for HTTPError

impl Display for SerialError

impl Display for TCPError

impl Display for WebRTCError

impl Display for WebSocketError

impl Display for WebSocketServerError

impl Display for Token

impl Display for ObserverError

impl Display for datex_core::references::reference::AccessError

impl Display for AssignmentError

impl Display for Reference

impl Display for ReferenceCreationError

impl Display for ReferenceMutability

impl Display for datex_core::references::reference::TypeError

impl Display for ScriptExecutionError

impl Display for ExecutionError

impl Display for InvalidProgramError

impl Display for DeserializationError

impl Display for SerializationError

impl Display for datex_core::type_inference::error::TypeError

impl Display for CollectionTypeDefinition

impl Display for TypeDefinition

impl Display for IllegalTypeError

impl Display for StructuralTypeDefinition

impl Display for CoreValue

impl Display for CallableKind

impl Display for Decimal

impl Display for DecimalTypeVariant

impl Display for TypedDecimal

impl Display for InvalidEndpointError

impl Display for NumberParseError

impl Display for IntegerTypeVariant

Trait Display