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Formulator

Created by . Last modified on 2003/09/12.

Formulator HOWTO

Introduction

This HOWTO is intended to give an introduction to the use of Formulator from the Zope Management Interface and from DTML, although much of this applies to use from ZPT or Python as well. Note that Formulator comes with online help for each tab as well as API help, so be sure to check that as well. This document will only give an overview of the possibilities and not all the details.

Formulator Scope

Formulator is a tool to create and validate web forms in Zope. Formulator takes care of the rendering of the fields in the form, as well as the validation and processing of the data that is submitted. Formulator's scope is limited to forms: "do web forms, web forms only, and web forms well." Formulator does currently not even take care of the precise layout of a form -- each form is layouted differently and thus layout is left to the developer. Formulator does allow for easy integration with external systems, however.

Creating a Formulator Form and Fields

It is easy to create a Formulator Form, just pick it from the add list and add it to a folder. I usually only have one form in a folder and call it form to make automatic layout handling easier; I'll say more about the reason for this later.

The default view of the form looks just like a folder, except that the only things that are addable are Formulator Fields. When you add a field to a form, it'll show up in the Form, just like an object shows up in a normal Zope Folder.

Fields

When you click on a field, you see a list of its properties in the field's Edit screen. This is a good time to explain that Formulator has an extensive help system, and that if you click on help in the Edit screen you'll see a list with a short description of what each property does.

If you click on the Test tab in the Field, you will see the field displayed as it would appear in the form. If you fill in some value in the field and click on the Test button, you can test its validation behavior. If everything could be validated and processed all right, you'll see the resulting value. If it could not be validated however, you see an error, showing the error_key and error_text.

The best way to learn about what the different fields do and how their properties work is to try them out. Just change some properties and see what happens in the Test screen. And be sure to look at the help.

Other Form tabs

The form Test tab is not difficult to explain; it shows all the fields you have added to the form. You can test the behavior of the entire form here.

In the Order part you can group fields and order them inside their groups. The order determines the order in which they appear on the Test screen, and can also can be used in your own code. Initially there is only a single Default group, but you can add new groups and change their names.

In the Settings tab you can determine the form properties. You can set the form submit action and method here, which you can later use with the header() and footer() methods of the form.

Other Field tabs

The field Override screen allows you to make the field call an override method (most commonly a Python Script) for a property. Instead of using the property value in the Edit screen, the method with the name listed in the override tab will be called to retrieve a value then. The returned value must be the same as the one that property's field generates; for an IntegerField this is an integer, for instance. The titles of overridden fields will be displayed between square brackets ([ ]) in the Edit screen.

In the Messages screen you can set the text of the error messages that field can generate upon validation errors.

On the examples in this HOWTO

All the examples in this HOWTO are contained in the file formulator_howto_examples.zexp, which you can download from the Formulator product page (http://www.zope.org/Members/faassen/formulator) and import into your Zope. In the examples, all the forms are called form.

Rendering a form manually with DTML (`manual` folder)

First, I will show how to use DTML to manually layout a form. This takes the most work, but also allows the most flexibility. In all these examples I will assume the form is called form.

The form contains three fields; a StringField animal, a StringField color, and an IntegerField number. index_html is the DTML Method that does the manual layout:

      <dtml-var standard_html_header>

      <!-- show the header of the form, using 'Form action' and 
        'Form method' form settings (<form action="..." method="...">)  
        -->
      <dtml-var "form.header()">

      <!-- a simple table for layout purposes -->
      <table border="0">

      <!-- each field will be on a line by itself -->

      <tr>
      <!-- first display the title property of the animal field -->
      <td><dtml-var "form.animal.get_value('title')"></td>
      <!-- render the field -->
      <td><dtml-var "form.animal.render()"></td>
      </tr>

      <!-- the same for the color field -->
      <tr>
      <td><dtml-var "form.color.get_value('title')"></td>
      <td><dtml-var "form.color.render()"></td>
      </tr>

      <!-- and the number field -->
      <tr>
      <td><dtml-var "form.number.get_value('title')"></td>
      <td><dtml-var "form.number.render()"></td>
      </tr>

      <!-- the submit button -->
      <tr>
      <td><input type="submit" value=" OK "></td>
      </tr>

      </table>

      <!-- the form footer -->
      <dtml-var "form.footer()">

      <dtml-var standard_html_footer>

This shows a form with the three fields. You can easily rearrange the layout just by changing the HTML.

Rendering a form automatically with DTML (`automatic` folder)

For many simple forms you don't need to do the layout yourself all the time. We can use Formulator and acquisition to make layout a lot easier. If we know each form is in a separate folder and is called form, we can place DTML method in the root of the site that can render any such form. In this example index_html will do the automated rendering directly. In real-world sites you'd usually use another method (for instance called form_body) to render because not all folders would contain forms. In that case it'd be easier to put the form rendering code in another method (for instance called form_body), which you can then call from your other code. Here's 'index_html':

      <dtml-var standard_html_header>

      <!-- show the header of the form, using 'Form action' and 
        'Form method' form settings (<form action="..." method="...">)  
        -->
      <dtml-var "form.header()">

      <!-- a simple table for layout purposes -->
      <table border="0">

      <!-- get a list of all fields in the form -->
      <dtml-in "form.get_fields()">
      <!-- rename each sequence item to 'field' so they can
           be used more easily -->
      <dtml-let field=sequence-item>

      <!-- each field will be on a line by itself -->    
      <tr>
      <!-- display the title property of this field -->
      <td><dtml-var "field.get_value('title')"></td>
      <!-- render the field -->
      <td><dtml-var "field.render()"></td>
      </tr>

      </dtml-let>
      </dtml-in>

      <!-- the submit button -->
      <tr>
      <td><input type="submit" value=" OK "></td>
      </tr>

      </table>

      <!-- the form footer -->
      <dtml-var "form.footer()">

      <dtml-var standard_html_footer>

The nice thing about the automatic approach is that now you can change the Formulator form as much as you like; this code will always automatically display them. Even better, if you add subfolders with forms in them, acquisition makes those forms display automatically as well! If you have only simple forms on a site, this could be the only DTML Method you need.

Form validation (`validation` folder)

I will use the same index_html as in the automatic form rendering example and the animal/color/number form to demonstrate form validation.

I've set the Form action property of the form to feedback. When the form is submitted it, Zope will access the feedback DTML Method. The form data will be coming into feedback in the REQUEST object (more precisely the REQUEST.form object).

The `feedback` method should do a number of things:

validate all fields (tell formulator to take care of this).
handle any validation errors.
if there were no validation errors, do something with the form results.

Here's feedback, with comments:

      <dtml-var standard_html_header>
      <dtml-try>
        <!-- try the validation, results should be put in
             REQUEST (keyed under the field id) --> 
        <dtml-call "form.validate_all_to_request(REQUEST)">  
      <dtml-except FormValidationError>
        <!-- if something went wrong with any field validation,
             a FormValidationError will be raised, which we
             will then catch here -->
        <!-- we will display the errors here -->
        <ul>
        <dtml-in "error_value.errors">
          <li>
          <dtml-var "field.get_value('title')">:
          <dtml-var error_text>
          </li>
        </dtml-in>
        </ul>

      <dtml-else>
        <!-- if no FormValidationError was raised, we're done
             with validation and our results will now be in
             REQUEST (and in DTML namespace). -->

        <!-- we could do anything with them, but we'll simply
             display them -->
        Hah, you are a <dtml-var color> <dtml-var animal> with
        <dtml-var number> legs.

      </dtml-try>

      <dtml-var standard_html_footer>

Note that often you can use acquisition with the validation page as well, so you can reuse most of its functionality.