[pmwiki-users] How do I check PTVs on other pages using conditional markup?

Peter Bowers pbowers at pobox.com
Mon May 14 06:21:46 CDT 2012

On Mon, May 14, 2012 at 8:32 AM, Martin Kerz <mkerz at me.com> wrote:
> yes, this comes from httpvariables. I want to access (and use) PTVs (in
> conditional markup) on the most recent page, as I am using jquery mobile
> dialogs.

OK, that clarifies what the markup is for.  Please see below.

> Am 11.05.2012 um 23:58 schrieb Peter Bowers:
> > On Fri, May 11, 2012 at 10:44 AM, Martin Kerz <mkerz at me.com> wrote:
> > (:if ( ! equal {={$?originpg}$:Prio} 0 ) :)
> > :Priority:{{$?originpg}$:Prio}
> > (:ifend:)

So after your httpvariable is interpolated with a value of
"Mygroup.Mypage" you would end up with a conditional that looks like

> > (:if ( ! equal {=Mygroup.Mypage$:Prio} 0 ) :)
> > :Priority:{Mygroup.Mypage$:Prio}
> > (:ifend:)

The use of the = in the first line indicates that you want it to get
the value from the current page in the pagelist.  But then you specify
the name of the page explicitly.  Perhaps you were looking for this:

> > (:if ( ! equal {=$:Prio} 0 ) :)
> > :Priority:{{$?originpg}$:Prio}
> > (:ifend:)

which says if the value of {$:Prio} on the current pagelist page is 0
then provide a default value from {Mygroup.Mypage$:Prio}

Do note that if this is an attempt to set a default value in a PTV
this does not work.  As recently discussed
(http://pmichaud.com/pipermail/pmwiki-users/2012-May/060230.html) you
cannot dynamically set PTVs via markup.  PTVs are read from the "raw"
text of your page, not from any marked-up version of the text.  Thus
any PTV definition you create by markup will *not* be read when you
try to read the PTV.

Capabilities such as this (dynamically setting PTVs) could
theoretically be requested via PITS, but the performance cost could be
astronomical.  Imagine doing a pagelist where you were listing a PTV
from each of a few hundred pages -- each page would have to be fully
rendered (i.e., all markup rules run) in the process of obtaining the
value of the PTV.  From a performance standpoint it would be
unthinkable unless you were going to try to cache PTV values or
something like that...

However, an alternate PTV markup which accepted a default value would
be quite do-able.  Basically you would choose your markup (stealing
from wikish [which of course in turn steals from bash] I would use
something like {$:varname:-DEFAULT VAL} ) and then you would create a
markup which would parse that markup, pass the $:varname to PageVar(),
check the return variable value and return either the variable value
or the default value depending on whether it was set/unset.

Here's the markup from stdmarkup.php

# {$var} substitutions
Markup('{$var}', '>$[phrase]',
  "PRR(PVSE(PageVar(\$pagename, '$2', '$1')))");

Although completely untested I think that something based off of this
might work:

# {$var:-dflt} substitutions
Markup('{$var:-default}', '<{$var}',
  "PRR(PVSE(PageVar(\$pagename, '$2', '$1') : ? '$3'))");

Do note that this will only work with the "val ?: alt" syntax from PHP
5.3 or beyond -- nothing prior to that
(http://www.php.net/manual/en/language.operators.comparison.php).  If
you're still on an earlier version then you'll need to assign a
variable or put it into a function or something...  If you want to put
a variable in as the default then you will want to change the order of
the rule to '>{$var}' or something...

Again, that's untested -- it probably won't work out of the box but
hopefully it points you in the right direction...

If you weren't trying to set a default value of a PTV then ignore all
my drivel above... :-)


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