Using Chunk Properties to Store Information

Many people are not aware the Chunks, like Snippets, have properties. These can be useful for displaying information.

I got to thinking about this when a MODX Forum user (playcock) asked about tags that would display the name and ID of the Chunk, like this: [[+chunkname]], [[+chunkid]] for a form that would appear after each section of page to allow the visitor to comment on whether the information in that section was useful or not. The forms would all be submitted to the same Snippet, so he needed a way for the Snippet to know which section was being rated. That meant each form had to be different and had to identify the Chunk related to the section above the form.

Since the sections were all Chunks, it made sense to include a Chunk tag at the end of each Chunk that would include the form with the name or ID of the Chunk used as a hidden input in the form.

Unfortunately, there are no such tags. I considered a custom Snippet, but there’s no way I know of to get those fields from inside the Chunk. You’d have to create a fairly elaborate Snippet that retrieved the Chunks and grabbed the two fields before displaying them.

You’d have to constantly edit the Snippet as pages changed and new Chunks were created. This would be particularly difficult since the individual Chunks could appear on multiple pages in different orders.

However, since Chunks have properties, you could create Chunk properties called chunkname and chunkid on the “Properties” tab when editing the Chunk. Then the tags above would work as expected.

Other Uses

There are a lot of ways to use Chunk properties. Your Chunks could contain all kinds of information that might change from time to time. The information might be sprinkled throughout the Chunk. If you edited the Chunk’s content each time, it would be easy to miss one.

For example, suppose you had a Chunk containing the officers of a large corporation. These would change from time to time, so it would very easy to use placeholder tags (like [[+propertyName]]) for each bit of information and add properties to the Chunk containing the information. The placeholder tags would have to match the names of the properties.

You could certainly put the information in the user’s Profile and write a Snippet to extract them and set the placeholders, but if you’re not comfortable writing PHP code, the properties would be a lot easier for you.

This technique has wider uses when you realize that Resources also have properties. They are seldom used, but page loads would be much faster if you used their properties rather than putting the information in Template Variables.

You’d lose the features of TVs, like @inherit and default values, so you can’t do away with TVs altogether with this technique, but it’s a good method to remember for when it’s appropriate.

Creating the Properties With a Snippet

If you have a lot of properties to create for a lot of Chunks (as in the original example above), you could automate the process with this simple Snippet. The Snippet will not affect existing Chunk properties other than the ones listed.

The Tag

After creating the Snippet, put this tag on a page, then view the page:

[[!AddChunkProperties]]

The Snippet Code

/* AddChunkProperties snippet */
$prefix = $modx->getVersionData()['version'] >= 3
    ? 'MODX\Revolution\\'
    : '';

$output = '';

/* Names of the chunks to process */

$chunks = array(
    'Chunk1',
    'Chunk2',
    'Chunk3',
    /* etc. */
);

/* Properties to be Added */

$newProperties = array(
    'Property1' => array(
        'name' => 'Property1', /* Nust match the value in the line above */
        'desc' => 'Property1 description',
        'type' => 'textfield',
        'value' => 'some value', /* could be empty: '' */
    ),
    'Property2' => array(
        'name' => 'Property2', /* Nust match the value in the line above */
        'desc' => 'Property2 description',
        'type' => 'textfield',
        'value' => 'some value', /* could be empty: '' */
    ),

    /* etc. */
);

foreach ($chunks as $chunkName) {
    $chunkObj = $modx->getObject($prefix . 'modChunk', 
        array('name' => $chunkName));

    if (!$chunkObj) {
        $output .= '<br>Could not find chunk: ' . $chunkName;
        continue;
    }

    $props = $chunkObj->get('properties');

    foreach ($newProperties as $newProperty) {
        $props[$newProperty['name']] = $newProperty;
    }
    $chunkObj->set('properties', $props);
    if (!$chunkObj->save()) {
        $output .= '<br> Could not save chunk: ' . $chunkName;
    } else {
        $output .= '<br> Set properties for chunk: ' . $chunkName;
        $output .= ' -- saved';
    }
}
return $output;

After running the Snippet, if you find a mistake in the results, you can edit the Snippet and run it again. You may need to clear the site cache and reload the Chunk page to see the changes.

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Bob Ray is the author of the MODX: The Official Guide and dozens of MODX Extras including QuickEmail, NewsPublisher, SiteCheck, GoRevo, Personalize, EZfaq, MyComponent and many more. His website is Bob’s Guides. It not only includes a plethora of MODX tutorials but there are some really great bread recipes there, as well.