Module icu::datetime::fieldsets::enums

Enumerations over field sets.

These enumerations can be used when the field set is not known at compile time. However, they may contribute negatively to the binary size of the formatters.

The most general type is CompositeFieldSet, which supports all field sets in a single enumeration. CompositeDateTimeFieldSet is a good choice when you don’t need to format time zones.

Summary of all the types:

Type	Supported Field Sets
DateFieldSet	Date
CalendarPeriodFieldSet	Calendar Period
TimeFieldSet	Time
ZoneFieldSet	Zone
DateAndTimeFieldSet	Date + Time
CompositeDateTimeFieldSet	Date, Calendar Period, Time, Date + Time
CompositeFieldSet	All

Examples

Format with the time display depending on a runtime boolean:

use icu::calendar::DateTime;
use icu::datetime::fieldsets;
use icu::datetime::fieldsets::enums::CompositeDateTimeFieldSet;
use icu::datetime::DateTimeFormatter;
use icu::locale::locale;
use writeable::Writeable;

fn get_field_set(should_display_time: bool) -> CompositeDateTimeFieldSet {
    if should_display_time {
        let field_set = fieldsets::MDT::medium().hm();
        CompositeDateTimeFieldSet::DateTime(
            fieldsets::enums::DateAndTimeFieldSet::MDT(field_set),
        )
    } else {
        let field_set = fieldsets::MD::medium();
        CompositeDateTimeFieldSet::Date(fieldsets::enums::DateFieldSet::MD(
            field_set,
        ))
    }
}

let datetime = DateTime::try_new_iso(2025, 1, 15, 16, 0, 0).unwrap();

let results = [true, false]
    .map(get_field_set)
    .map(|field_set| {
        DateTimeFormatter::try_new(locale!("en-US").into(), field_set)
            .unwrap()
    })
    .map(|formatter| formatter.format_any_calendar(&datetime).to_string());

assert_eq!(results, ["Jan 15, 4:00 PM", "Jan 15"])

Enums

• CalendarPeriodFieldSet
  An enumeration over all possible calendar period field sets.
• CompositeDateTimeFieldSet
  An enum supporting date, calendar period, time, and date+time field sets and options.
• CompositeFieldSet
  An enum supporting all possible field sets and options.
• DateAndTimeFieldSet
  An enumeration over all possible date+time composite field sets.
• DateFieldSet
  An enumeration over all possible date field sets.
• TimeFieldSet
  An enumeration over all possible time field sets.
• ZoneFieldSet
  An enumeration over all possible zone field sets.