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.
§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 · Sourcefn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>
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, }),
);Implementors§
impl Display for wiwi::encoding::hex::DecodeError
impl Display for wiwi::encoding::z85::DecodeError
impl Display for Infallible
impl Display for VarError
impl Display for AsciiChar
impl Display for IpAddr
impl Display for SocketAddr
impl Display for ErrorKind
impl Display for RecvTimeoutError
impl Display for std::sync::mpsc::TryRecvError
impl Display for RoundingError
impl Display for Weekday
impl Display for bool
impl Display for char
impl Display for f32
impl Display for f64
impl Display for i8
impl Display for i16
impl Display for i32
impl Display for i64
impl Display for i128
impl Display for isize
impl Display for !
impl Display for str
impl Display for u8
impl Display for u16
impl Display for u32
impl Display for u64
impl Display for u128
impl Display for usize
impl Display for wiwi::prelude_std::alloc_mod::AllocError
impl Display for LayoutError
impl Display for TryFromSliceError
impl Display for BorrowError
impl Display for BorrowMutError
impl Display for JoinPathsError
impl Display for Location<'_>
impl Display for PanicHookInfo<'_>
impl Display for ParseBoolError
impl Display for Utf8Error
impl Display for FromUtf8Error
impl Display for FromUtf16Error
impl Display for String
impl Display for UnorderedKeyError
impl Display for alloc::collections::TryReserveError
impl Display for FromVecWithNulError
impl Display for IntoStringError
impl Display for NulError
impl Display for core::ascii::EscapeDefault
impl Display for CharTryFromError
impl Display for ParseCharError
impl Display for DecodeUtf16Error
impl Display for core::char::EscapeDebug
impl Display for core::char::EscapeDefault
impl Display for core::char::EscapeUnicode
impl Display for ToLowercase
impl Display for ToUppercase
impl Display for TryFromCharError
impl Display for FromBytesUntilNulError
impl Display for FromBytesWithNulError
impl Display for Ipv4Addr
impl Display for Ipv6Addr
Writes an Ipv6Addr, conforming to the canonical style described by RFC 5952.
impl Display for AddrParseError
impl Display for SocketAddrV4
impl Display for SocketAddrV6
impl Display for core::num::dec2flt::ParseFloatError
impl Display for ParseIntError
impl Display for TryFromIntError
impl Display for PanicInfo<'_>
impl Display for PanicMessage<'_>
impl Display for TryFromFloatSecsError
impl Display for Backtrace
impl Display for std::ffi::os_str::Display<'_>
impl Display for WriterPanicked
impl Display for std::io::error::Error
impl Display for std::path::Display<'_>
impl Display for StripPrefixError
impl Display for ExitStatus
impl Display for ExitStatusError
impl Display for std::sync::mpsc::RecvError
impl Display for AccessError
impl Display for SystemTimeError
impl Display for ParseError
impl Display for ParseMonthError
impl Display for NaiveDate
The Display output of the naive date d is the same as
d.format("%Y-%m-%d").
The string printed can be readily parsed via the parse method on str.
§Example
use chrono::NaiveDate;
assert_eq!(format!("{}", NaiveDate::from_ymd_opt(2015, 9, 5).unwrap()), "2015-09-05");
assert_eq!(format!("{}", NaiveDate::from_ymd_opt(0, 1, 1).unwrap()), "0000-01-01");
assert_eq!(format!("{}", NaiveDate::from_ymd_opt(9999, 12, 31).unwrap()), "9999-12-31");ISO 8601 requires an explicit sign for years before 1 BCE or after 9999 CE.
assert_eq!(format!("{}", NaiveDate::from_ymd_opt(-1, 1, 1).unwrap()), "-0001-01-01");
assert_eq!(format!("{}", NaiveDate::from_ymd_opt(10000, 12, 31).unwrap()), "+10000-12-31");impl Display for NaiveDateTime
The Display output of the naive date and time dt is the same as
dt.format("%Y-%m-%d %H:%M:%S%.f").
It should be noted that, for leap seconds not on the minute boundary, it may print a representation not distinguishable from non-leap seconds. This doesn’t matter in practice, since such leap seconds never happened. (By the time of the first leap second on 1972-06-30, every time zone offset around the world has standardized to the 5-minute alignment.)
§Example
use chrono::NaiveDate;
let dt = NaiveDate::from_ymd_opt(2016, 11, 15).unwrap().and_hms_opt(7, 39, 24).unwrap();
assert_eq!(format!("{}", dt), "2016-11-15 07:39:24");Leap seconds may also be used.
let dt =
NaiveDate::from_ymd_opt(2015, 6, 30).unwrap().and_hms_milli_opt(23, 59, 59, 1_500).unwrap();
assert_eq!(format!("{}", dt), "2015-06-30 23:59:60.500");impl Display for NaiveTime
The Display output of the naive time t is the same as
t.format("%H:%M:%S%.f").
The string printed can be readily parsed via the parse method on str.
It should be noted that, for leap seconds not on the minute boundary, it may print a representation not distinguishable from non-leap seconds. This doesn’t matter in practice, since such leap seconds never happened. (By the time of the first leap second on 1972-06-30, every time zone offset around the world has standardized to the 5-minute alignment.)
§Example
use chrono::NaiveTime;
assert_eq!(format!("{}", NaiveTime::from_hms_opt(23, 56, 4).unwrap()), "23:56:04");
assert_eq!(
format!("{}", NaiveTime::from_hms_milli_opt(23, 56, 4, 12).unwrap()),
"23:56:04.012"
);
assert_eq!(
format!("{}", NaiveTime::from_hms_micro_opt(23, 56, 4, 1234).unwrap()),
"23:56:04.001234"
);
assert_eq!(
format!("{}", NaiveTime::from_hms_nano_opt(23, 56, 4, 123456).unwrap()),
"23:56:04.000123456"
);Leap seconds may also be used.
assert_eq!(
format!("{}", NaiveTime::from_hms_milli_opt(6, 59, 59, 1_500).unwrap()),
"06:59:60.500"
);