VarQUERY < System < Iris Wiki

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---+ QUERY -- get the value of meta-data
Uses the query syntax described in [[%SYSTEMWEB%.QuerySearch][QuerySearch]] to get information about meta-data from one specified topic.
   * supports formatted access to formfields and other meta-data in  topics using the same syntax as is used in =IF= and =SEARCH= statements,
   * gives access to *all* meta-data, including that added by extensions,
   * supports reporting values using JSON and other standards, simplifying the retrieval of meta-data for REST applications,
   * replaces the =[[VarFORMFIELD][FORMFIELD]]= macro for most applications.
See !QuerySearch for more details of how to write queries
---++ Parameters
   | *Parameter* | *Description* | *Default* |
   | ="item"= | The meta-data to query |
   | =style= | set the output format (see below) |
   | =rev= | operate on the given version of the current topic. Note that this will _only_ affect simple queries that refer to the current topic, such as =form.name=. More complex queries that use searches or indirection to refer to other topics always use the *latest* version of those topics. |

---++ Examples
<pre class="tml">
      Get the name of the form in the current topic:
      %<nop>QUERY{"form.name"}%

      Get the value of the 'Firstname' form field in
        the current topic:
      %<nop>QUERY{"fields[name='Firstname'].value"}%

      Get the value of the 'Firstname' form field in
        the current topic (shorthand version):
      %<nop>QUERY{"Firstname"}%

      Get a list of all the names of attachments on
        the topic '%SYSTEMWEB%.DocumentGraphics':
      %<nop>QUERY{"'%SYSTEMWEB%.DocumentGraphics'/attachments.name"}%

      Get configuration setting {NameFilter}:
      %<nop>QUERY{"{NameFilter}"}%
</pre>
Plain strings (such as field values) are returned _without_ quotes. Simple arrays of scalars are also returned without quotes, in a comma-separated list (beware of values that contain commas!).

More complex data structures (e.g. arrays of hashes) will only be returned if =style="perl"= or =style="json"= are set - else will return a string containing 'undef'.

You can make the macro generate different output formats using the =style= parameter:
   * =style="perl"= - generates values as Perl code strings generated by running through CPAN:Data::Dumper
   * =style="json"= - generates values as JSON strings, suitable for reading by browsers.

Only some configuration settings are available via QUERY: %FORMAT{"%QUERY{"{AccessibleCFG}"}%" type="string" format="=$item=" separator=", "}%

%STOPINCLUDE%
---++ Related
 [[VarMETA][META]] [[QuerySearch][QuerySearch]]
<!--%JQREQUIRE{"chili"}%-->

Topic revision: r1 - 20 Dec 2016, ProjectContributor

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