MessageFormat class
MessageFormat grammar:
message := messageText (argument messageText)*
argument := simpleArg | pluralArg | selectArg
simpleArg := "#" | "{" argNameOrNumber "}"
pluralArg := "{" argNameOrNumber "," "plural" "," pluralStyle "}"
selectArg := "{" argNameOrNumber "," "select" "," selectStyle "}"
argNameOrNumber := identifier | number
pluralStyle := [offsetValue] (pluralSelector "{" message "}")+
offsetValue := "offset:" number
pluralSelector := explicitValue | pluralKeyword
explicitValue := "=" number // adjacent, no white space in between
pluralKeyword := "zero" | "one" | "two" | "few" | "many" | "other"
selectStyle := (selectSelector "{" message "}")+
selectSelector := keyword
identifier := [^[[:Pattern_Syntax:][:Pattern_White_Space:]]]+
number := "0" | ("1".."9" ("0".."9")*)
NOTE: "#" has special meaning only inside a plural block. It is "connected" to the argument of the plural, but the value of # is the value of the plural argument minus the offset.
Quoting/Escaping: if syntax characters occur in the text portions, then they need to be quoted by enclosing the syntax in pairs of ASCII apostrophes.
A pair of ASCII apostrophes always represents one ASCII apostrophe, similar to %% in printf representing one %, although this rule still applies inside quoted text.
("This '{isn''t}' obvious" → "This {isn't} obvious")
An ASCII apostrophe only starts quoted text if it immediately precedes a character that requires quoting (that is, "only where needed"), and works the same in nested messages as on the top level of the pattern.
Recommendation: Use the real apostrophe (single quote) character ’ (U+2019) for human-readable text, and use the ASCII apostrophe ' (U+0027) only in program syntax, like escaping.
This is a subset of the ICU MessageFormat syntax: http://userguide.icu-project.org/formatparse/messages.
Message example:
I see {NUM_PEOPLE, plural, offset:1
=0 {no one at all}
=1 {{WHO}}
one {{WHO} and one other person}
other {{WHO} and # other people}}
in {PLACE}.
Calling format({'NUM_PEOPLE': 2, 'WHO': 'Mark', 'PLACE': 'Athens'})
would
produce "I see Mark and one other person in Athens."
as output.
Calling format({'NUM_PEOPLE': 5, 'WHO': 'Mark', 'PLACE': 'Athens'})
would
produce "I see Mark and 4 other people in Athens."
as output.
Notice how the "#" is the value of NUM_PEOPLE
- 1 (the offset).
Another important thing to notice is the existence of both "=1"
and
"one"
. You should think of the plural keywords as names for "buckets of
numbers" which have only a loose connection to the numerical value.
In English there is no difference, but for example in Russian all the
numbers that end with "1"
but not with "11"
are mapped to "one"
For more information please visit: http://cldr.unicode.org/index/cldr-spec/plural-rules and http://www.unicode.org/cldr/charts/latest/supplemental/language_plural_rules.html
Constructors
- MessageFormat(String pattern, {String locale = 'en'})
-
Create a MessageFormat for the ICU message string
pattern
. It does parameter substitutions in a locale-aware way. The syntax is similar to the one used by ICU and is described in the grammar above.
Properties
- hashCode → int
-
The hash code for this object.
no setterinherited
- runtimeType → Type
-
A representation of the runtime type of the object.
no setterinherited
Methods
-
format(
[Map< String, Object> ? namedParameters]) → String - Returns a formatted message, treating '#' as a special placeholder.
-
formatIgnoringPound(
[Map< String, Object> ? namedParameters]) → String - Returns a formatted message, treating '#' as literal character.
-
noSuchMethod(
Invocation invocation) → dynamic -
Invoked when a nonexistent method or property is accessed.
inherited
-
toString(
) → String -
A string representation of this object.
inherited
Operators
-
operator ==(
Object other) → bool -
The equality operator.
inherited