predicate expression - searching for records that have an empty field
  • Vote Up0Vote Down michaelmichael December 2011

    Is it possible to use predicate expressions to filter out entries in a collection that have content? For example, in this collection I want to filter out the entries that have an empty 'swf' textarea field.

    <v:collection path="holes" paginate="10">
    <v:img path="thumbnail" width="620" height="620"/>
    </v:collection>

    I am trying to filter out all records that have embed code data I tried this, but it did not work

    <v:collection path="holes[swf=='']" paginate="10">
    <v:img path="thumbnail" width="620" height="620"/>
    </v:collection>

    However, the opposite query does work

    <v:collection path="holes[swf!='']" paginate="10">
    <v:img path="thumbnail" width="620" height="620"/>
    </v:collection>

    So I am confused.

  • 4 Answers sorted by
  • Vote Up0Vote Down Scott December 2011

    Hey Mike. Could you use the v:if tag?

    <v:collection path="holes" paginate="10">
    <v:if path="swf">
    <v:img path="thumbnail" width="620" height="620"/>
    <v:if>
    </v:collection>

  • Vote Up0Vote Down michaelmichael December 2011

    No, in this case the filtering has to be done in the collection tag.

  • Vote Up0Vote Down KevinKevin December 2011

    Not sure on this.

    Try:
    path="holes[not(swf)]"

    This is a weird edge case in xpath (VaeQL is based on XPath) because you aren't looking for a blank node, you're looking for a node that doesn't exist at all. (Because we don't store blank nodes in memory.)

    Let me know if that works and if it doesn't drop me an email at [email protected]

  • Vote Up0Vote Down michaelmichael December 2011

    path="holes[not(swf)]"

    Does not work in Vae even though it is part of xpath. This should be implemented in the future.

    The solution I came up with was creating a JSON object loaded via ajax that was then parsed as an object literal in Javascript depending on the values of the user agent and the 'swf' key.

    Then it was appended to the DOM and bam it did what I needed it to do.

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