At the Forge - CMF Types

Over the last few months, we have discussed content management systems (CMS) in general and Zope's content management framework (CMF) in particular. Zope's CMF is designed to give developers the tools they need to create their own content management systems. Of course, anyone who has worked with a CMS knows that even the most proprietary of the bunch requires extensive modification, reworking and customization before it can be used. Zope thus not only reduces the price of the base software, but provides a rich environment that makes it relatively easy to develop and customize the CMS.

When you create a CMF site, you (as the site manager) can add, modify and delete documents. Click on the folder contents link, click on the New... button, indicate which type of document you want to add and what ID it should have and then click on the add button. Enter the metadata (that is, title, description, subject and content type), click on the change & edit button, add some content and you're off and running.

However, although the existing content types are sufficient for simple sites, more sophisticated sites will want to create their own, custom types. CMF provides several ways to do exactly this. This month, we look at types in CMF—how we can work with them, customize their behavior, install new ones and even create new types to handle custom content.

The simplest way to create a new type is to use CMF's built-in, Web-based type extension system. It allows you to create a new type that shares its methods, properties, actions, presentation templates and icons with another type by default. When you create a new type using the Web-based extension system, you can modify any of these items, except for the methods and properties. In other words, the new type you create can have a different look and feel from its parent type, but it continues to behave much as the parent did.

For example, let's go to what is known as the types tool, available by clicking on portal_types within the management interface for a CMF site. If you don't have a CMF site already defined in Zope, you can create one by choosing CMF Site from the Add... menu in the upper-right corner of the Web-based Zope management interface. Once you have created the site, clicking on its icon from within the management interface displays a number of different customization tools, each with an icon that looks like a wrench.

When you first enter the types tool, you see a list of the currently defined CMF types, including folders, documents, news items, links and topics. You can examine and modify the properties and actions associated with these types by clicking on the name of the type you want to change. For example, if you want to examine or change the way the File content type does things, click on File. This brings up a new set of management tabs at the top of the page, with properties (the default) and actions being the only ones not standard to other parts of Zope. Actually, properties is a standard Zope tab, but CMF types have a number of unusual property names.

In addition to the standard properties you expect to see, each type has the following properties that affect what it does: