Why learn how to use a new framework?


You may be wondering why should you learn how to use a new forms framework if you already know how to use the CMF Form Controller Tool (Form Controller).

Why should you use a forms framework at all? You could always write your own HTML form snippets and use the request dictionary to retrieve and handle data.

The reason is simple: you'll end up writing a lot of boilerplate code to collect, validate and build the response. It would be better if you could just define the fields and metadata of the form and re-use a set of base classes to do the repetitive work behind the scenes, i.e., a forms framework.

One of these frameworks is the Form Controller Tool, which is not bad, but has some disadvantages over formlib:

  • First, the Form Controller spreads the form logic across several files so it can be hard to follow it.
  • Second, the From Controller doesn't handle the creation and display of the widgets, so you have to create them manually, what could become especially unmantainable when using choice-type fields.
  • Last, the Form Controller doesn't work with Zope 3 schema interfaces nor views. Using a Zope 3 schema can help you creating add and edit forms.

However, the Form Controller can be useful and even preferable when you need to implement a complex page flow, or if you want to customize Plone forms that use it; e.g. the ''Send this page to someone'' form.

Beginning with Zope 2.9.3 (Plone 2.5) zope.formlib is being distributed with Zope 2. Five >= 1.4 is required to make use of this Zope 3 package.

Note: Where do I place the code?

You can place the code wherever you want: all in the same file, each class in a file, in several directories, utilities in a utilities.py file, etc. Just keep in mind two things:

  • If you write several pieces of code (functions, classes) in separate files, remember to import them whenever you use them, as you would do in any other Python program.
  • The ZCML statements have to be placed into a file called configure.zcml in the root of your package, or in any other file included from it.

Said that, the author reccommends putting all the Python code in a file named browser.py in this tutorial to avoid confusion.