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#1 2018-08-20 08:12:13

jakob
Moderator
From: Germany
Registered: 2005-01-20
Posts: 3,228
Website

Problems using if_different in a plugin

I’m attempting to resurrect mka_ical and wanted to add if_first, if_last and if_different functionality. The first two I’ve managed but only by introducing new tags/functions for those as an event list is not an article context, so the existing functions won’t work.

Looking at the code for if_different, it looks as if that code should work in any loop context, but I’m getting mixed success.

mka_ical uses placeholders – {start_date}, {end_date}, {title} etc. – and if I use them in a form with if_different like the following snippet, this works:

<txp:mka_ical url="testfile.ics">
<txp:if_different><h5 class="dt-start">{start_date}</h5></txp:if_different>
<p><span class="dt-end">{start_time}</span> – <span class="p-summary">{title}</span></p>
</txp:mka_ical>

I get just each new date listed and the times on that day listed beneath it without repeating the date.

mka_ical has a format attribute for times but only for everything. I’ve added a simple additional tag to the plugin to make it possible to reformat date output as follows:

function mka_format_date($atts, $thing = '')
{
    extract(lAtts(array(
        'format' => ''
    ), $atts, false));

    if ($format === '') {
        return $thing;
    } else {
        return strftime($format, strtotime($thing));
    }
}

When I use this tag in if_different, for example to show a heading at the beginning of each year (or month), it doesn’t work:

<txp:mka_ical url="testfile.ics">
<txp:if_different><h3><txp:mka_format_date format="%Y">{start_date}</txp:mka_format_date></h3></txp:if_different>
<txp:if_different><h5 class="dt-start">{start_date}</h5></txp:if_different>
<p><span class="dt-end">{start_time}</span> – <span class="p-summary">{title}</span></p>
</txp:mka_ical>

I get a year heading for every new {start_date}.

However, if I first write the result into a variable and then do if_different on the variable, I can trick it into working:

<txp:mka_ical url="testfile.ics">
<txp:variable name="start_year"><txp:mka_format_date format="%Y">{start_date}</txp:mka_format_date></txp:variable>
<txp:if_different><txp:variable name="start_year" wraptag="h3" /></txp:if_different>
<txp:if_different><h5 class="dt-start">{start_date}</h5></txp:if_different>
<p><span class="dt-end">{start_time}</span> – <span class="p-summary">{title}</span></p>
</txp:mka_ical>

What do I need to change in my function to make if_different notice the output of the function, and not the {start_date} item being reformatted?

Or do I need a custom if_different function? And if so, what has to be different?


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#2 2018-08-20 15:04:33

etc
Developer
Registered: 2010-11-11
Posts: 3,017
Website

Re: Problems using if_different in a plugin

Interesting case. The values stored by if_different are indexed by md5 hashes of their unparsed content. So,

<txp:if_different><txp:variable name="start_year" wraptag="h3" /></txp:if_different>

will always use d41d8cd98f00b204e9800998ecf8427e key (i.e. md5('<txp:variable name="start_year" wraptag="h3" />')) to store the last value of <txp:variable name="start_year" wraptag="h3" />. But

<txp:if_different><h3><txp:mka_format_date format="%Y">{start_date}</txp:mka_format_date></h3></txp:if_different>

will use a new key as soon as {start_date} is changed, so a new value of <h3><txp:mka_format_date format="%Y">{start_date}</txp:mka_format_date></h3> will not be compared with a previous one (unless dates are identical).

Dunno what is the best way to fix it. An easy one is to introduce some id (or key or hash) attribute to <txp:if_different />.


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#3 2018-08-20 21:20:07

jakob
Moderator
From: Germany
Registered: 2005-01-20
Posts: 3,228
Website

Re: Problems using if_different in a plugin

Thanks for the feedback Oleg. That was my conclusion too, though I wasn’t sure of the reason. For the moment I’m using the txp:variable workaround which works, but it’s not really a good solution. It would be much better if the plugin responded as one would expect it to.

Could I :

a) make a separate mka_if_different tag that adds that extra hash/id attribute. Could you fill me in with what that’s supposed to do?

b) Currently I’ve kept the {placeholder} items so as not to move too far away from the existing plugin. One could create a tag to output the items much like txp:image_info does for images but it breaks backwards compatibility. An own tag would almost certainly then work with if_different, no?

At present, the {placeholders} correspond more-or-less directly to the items in the ical feed/functions in the ical parser library with just {start_date} / {start_time} and the end equivalents being put through a date formatter which uses the tag’s fmtdate and fmttime attributes (which is global for an entire calendar). That was all in the plugin already. I added {start_datetime} and {end_datetime} with fixed formatting for use with the html datetime attribute as that has to have a predefined format even if dates are displayed differently to visitors. They serve a common need/scenario. I guess one could create {start_year}, {start_month}, {start_day} etc. placeholders, so that if_different acts on a preformatted item but it quickly gets long-winded as you try to cover ever more situations, so it’s not particularly elegant. I wonder whether the might be a way to incorporate date formatting directly into the placeholder item (that is hashed by if_different), but I’m not sure how?


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#4 2018-08-21 17:10:53

etc
Developer
Registered: 2010-11-11
Posts: 3,017
Website

Re: Problems using if_different in a plugin

jakob wrote #313545:

Could I :

a) make a separate mka_if_different tag that adds that extra hash/id attribute. Could you fill me in with what that’s supposed to do?

function mka_if_different($atts, $thing)
{
    static $last = array();

    extract(lAtts(array('key' => md5($thing)), $atts));
//    $key = md5($thing);
    $out = parse($thing, 1);

    if (empty($last[$key]) || $out != $last[$key]) {
        return $last[$key] = $out;
    } else {
        return parse($thing, 0);
    }
}

You then can fix a key of the last array that will be used for comparison:

<txp:mka_if_different key="start_date">
<h3><txp:mka_format_date format="%Y">{start_date}</txp:mka_format_date></h3>
</txp:mka_if_different>

b) Currently I’ve kept the {placeholder} items so as not to move too far away from the existing plugin. One could create a tag to output the items much like txp:image_info does for images but it breaks backwards compatibility. An own tag would almost certainly then work with if_different, no?

If this new tag is processed in the normal flow (from outside to inside), then yes. The problem with placeholders is that they are filled before the surrounding tags are parsed.


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#5 2018-08-21 17:24:39

etc
Developer
Registered: 2010-11-11
Posts: 3,017
Website

Re: Problems using if_different in a plugin

Just for the record, in

<txp:if_different>
<txp:php>echo 2*2;</txp:php>
</txp:if_different>

<txp:if_different>
<txp:php>echo 2*2;</txp:php>
</txp:if_different>

only the first tag will output 4. But

<txp:if_different>
<txp:php>echo 2*2;</txp:php>
</txp:if_different>

<txp:if_different>
<txp:php>echo 2+2;</txp:php>
</txp:if_different>

will both output 4, even if the results are identical.


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#6 2018-08-21 22:31:52

jakob
Moderator
From: Germany
Registered: 2005-01-20
Posts: 3,228
Website

Re: Problems using if_different in a plugin

Thanks Oleg. That does it.

I understand from your example, that it’s hashing the method and not the output. I’ll experiment some more but I think I have it working now.


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