Returning empty string when attribute does not match return text when attribute matches

Question

I need to be able to keep track of where in the document any particular value is. I would use XSL but the ecosystem I'm working in prevents that. I'm using the Java Saxon-HE 9.7.0-2 processor.

XML

<test>
    <value cat="fiction">At the edge of the orchard</value>
    <value cat="mythology">Hero with a thousand faces</value>
    <value cat="fiction">Spill simmer falter wither</value>
</test>

XPath

for $a in /test
    return
        (if ($a/value[@cat="mythology"]) then 
            $a/value[@cat="mythology"] else
            "")

What I would like to see come back is:

""
"Hero with a thousand faces"
""

What I'm currently seeing is:

"Hero with a thousand faces"

Link to videlibri xpath tester

Link to saxon code

Linga Murthy C S · Accepted Answer · 2016-09-13 00:39:51Z

1

I think you want to iterate on every value and do the check. The below xpath should work for you:

string-join((for $a in /test/value
                                return
                                    (if ($a[@cat='mythology']) then 
                                        concat('&quot;',$a,'&quot;') else
                                        '&quot;&quot;')),'&#xa;')

Simplified:

string-join((for $a in /test/value
            return
                concat('&quot;',($a[@cat='mythology'],'')[1], '&quot;'))
     ,'&#xa;')

answered Sep 13, 2016 at 0:39

Linga Murthy C S

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1 Comment

BDF Over a year ago

Thank you; it is closer to what I need but now I'm in the position of having a to parse the return. What I get with this xPath is: ""
"Hero with a thousand faces"
"" Parsing that is risky for me because in reality what is in that block of text is unconstrained. I still may have to go with this solution if I can't come up with something better.

BDF · Accepted Answer · 2016-09-13 14:46:28Z

0

This is returning the empty strings I'm looking for:

for $a in /test/value
return
    if ($a[@cat='mythology']) then 
        $a[@cat='mythology'] else
        ""

Can someone explain why this xpath behaves differently from the one in the original question?

videlibri xpath tester

edited Sep 13, 2016 at 14:46

answered Sep 13, 2016 at 14:04

BDF

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1 Comment

BDF Over a year ago

To answer my own question: The original loop of 'for $a in /test' is only one node so the containing if statement only ever gets evaluated once. In the version that works; I'm iterating over multiple nodes. This was made clear to me when I evaluated /test/value[@cat='fiction'] by itself without the loop and if statements. Another thank you for lingamurthy for getting me down the right path.

Martin Honnen · Accepted Answer · 2016-09-14 12:05:33Z

0

I think /test/value/(.[@cat = 'mythology'], '')[1] suffices and is a bit more compact than the for .. return if ... then ... else.

edited Sep 14, 2016 at 12:05

answered Sep 14, 2016 at 11:21

Martin Honnen

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