addFlag method
Defines a boolean flag.
This adds an Option with the given properties to options.
The abbr
argument is a single-character string that can be used as a
shorthand for this flag. For example, abbr: "a"
will allow the user to
pass -a
to enable the flag.
The help
argument is used by usage to describe this flag.
The defaultsTo
argument indicates the value this flag will have if the
user doesn't explicitly pass it in.
The negatable
argument indicates whether this flag's value can be set to
false
. For example, if name
is flag
, the user can pass --no-flag
to set its value to false
.
The callback
argument is invoked with the flag's value when the flag
is parsed. Note that this makes argument parsing order-dependent in ways
that are often surprising, and its use is discouraged in favor of reading
values from the ArgResults.
If hide
is true
, this option won't be included in usage.
If aliases
is provided, these are used as aliases for name
. These
aliases will not appear as keys in the options map.
Throws an ArgumentError if:
- There is already an option named
name
. - There is already an option using abbreviation
abbr
.
Implementation
void addFlag(String name,
{String? abbr,
String? help,
bool? defaultsTo = false,
bool negatable = true,
void Function(bool)? callback,
bool hide = false,
List<String> aliases = const []}) {
_addOption(
name,
abbr,
help,
null,
null,
null,
defaultsTo,
callback == null ? null : (bool value) => callback(value),
OptionType.flag,
negatable: negatable,
hide: hide,
aliases: aliases);
}