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@---+ Package =TWiki::Attrs=
Class of attribute sets, designed for parsing and storing attribute values
from a TWiki tag e.g. =%TAG{fred='bad' "sad" joe="mad"}%=

An attribute set is a map containing an entry for each parameter. The
default parameter (unnamed quoted string) is named <code>_<nop>DEFAULT</code> in the map.

Attributes declared later in the string will override those of the same
name defined earlier. The one exception to this is the _DEFAULT key, where
the _first_ instance of a setting is always taken.

As well as standard TWiki syntax (parameter values double-quoted)
it also parses single-quoted values, unquoted spaceless
values, spaces around the =, and commas as well as spaces separating values,
though none of these alternatives is advertised in documentation and
the extended syntax can be turned off by passing the 'strict' parameter
to =new=.

This class replaces the old TWiki::extractNameValuePair and
TWiki::extractParameters.


%TOC%

---++ ClassMethod *new* <tt>($string,$friendly)=>\%attrsObjectRef</tt>
   * =$string= - String containing attribute specification
   * =$friendly= - if true, the parse will be according to the extended syntax pioneered by the original Contrib::Attrs. Otherwise it will be strict as per traditional TWiki syntax.

Parse a standard attribute string containing name=value pairs and create a new
attributes object. The value may be a word or a quoted string. If there is an
error during parsing, the parse will complete but $attrs->{_ERROR} will be
set in the new object. $attrs->{_RAW} will always contain the full unprocessed
$string.

Extended syntax example:
<verbatim>
my $attrs = new TWiki::Attrs('the="time \\"has come", "the walrus" said to=speak of=\'many \\'things\', 1);
</verbatim>
In this example:
   * =the= will be =time "has come=
   * <code>_<nop>_<nop>default__</code> will be =the walrus=
   * =said= will be =on=
   * =to= will be =speak=
   * =of= will be =many 'things=

Only " and ' are escaped.

Traditional syntax is as old TWiki, except that the whole string is parsed
(the old parser would only recognise default values in position 1, nowhere
else)



---++ ObjectMethod *isEmpty* <tt>() -> boolean</tt>
Return false if attribute set is not empty.



---++ ObjectMethod *remove* <tt>($key) -> $value</tt>
| $key | Attribute to remove |
Remove an attr value from the map, return old value. After a call to
=remove= the attribute is no longer defined.



---++ ObjectMethod *stringify* <tt>() -> $string</tt>
Generate a printed form for the map, using standard
attribute syntax, with only the single-quote extension
syntax observed (no {} brackets, though).



---++ StaticMethod *extractValue* <tt>() -> $string</tt>
Legacy support, formerly known as extractNameValuePair. This
static method uses context information to determine how a value
string is to be parsed. For example, if you have an attribute string
like this:

"abc def="ghi" jkl" def="qqq"

then call extractValue( "def" ), it will return "ghi".




---++ ObjectMethod *get* <tt>($key) -> $value</tt>
| $key | Attribute to get |
Get an attr value from the map.

Synonymous with $attrs->{$key}. Retained mainly for compatibility with
the old AttrsContrib.


@
