(Tips) Creating a Compound Field Module for CCK in Drupal 6.x

Tips : Creating a Compound Field Module for CCK in Drupal 6.x

When setting up a site using the Drupal content management system, you'll often find that you need to define content types that have fields attached to them, beyond the default Title and Body. In Drupal version 7.x and later, this field functionality is planned to be in the core distribution of Drupal, but in 6.x and previous versions of Drupal, it is provided by the contributed Content Construction Kit (CCK) module and the many associated modules that provide additional field types for CCK.

For some sites, you may find that you need to define fields that have multiple values; for example, you might want to place several images along the right side of a page (each one being an Image field). That is no problem, in itself -- CCK allows you to set any field to accept multiple values, and in version 2 of CCK, you can easily re-order, delete, and add new items to the list using a very nice AJAX interface.

But what if you need to associate, for instance, a caption and a taxonomy term with each of those images? With the current CCK version, you have several choices:

1. Create a multiple-valued field for the image, another for the caption, and another for the taxonomy term, and tell the people editing content on the site to try to keep them synchronized. This is not really workable in general -- users would need to scroll up and down the content entry screen to do their data entry, and inevitably someone will make a mistake and you'll have a caption or term associated with the wrong image. Also, for this specific case, Content Taxonomy as a multiple-valued field just gives you one multi-select list, so there is no way to choose a given taxonomy term more than once, or indicate the order (term 1 goes with image 1, etc.)

2. Create a second content type "Image Caption Term" to hold an image and its associated data. Then add a multiple "Node Reference" field to your original content type, which will associate your page with its images. This can be made to work, but in practice the editing is at best clumsy. Also, you'll end up with a lot of these little "Image Caption Term" items cluttering up your content management screens, which will confuse novice users.

3. Try out an experimental "Content Multigroup" module that is supposed to let you group multiple CCK fields together. As of this writing (February 2009), this module is not stable (not even released as an "alpha" version), and last time I tried it (October 2008), it didn't work at all with image fields.

4. Create your own custom CCK field module that contains the desired grouping of information. Doing this is not very difficult, works very well, and is the subject of this article.

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Courtesy:- poplarware.com