Using Form Builder: building html forms dynamically


($‌Id: form-builder.xml,v 2019/03/10 21:44:57 gustafn Exp $)
OpenACS docs are written by the named authors, and may be edited by OpenACS documentation staff.

OpenACS has a form manager called ad_form. Ad_form has an adaptable UI. Error handling includes inline error reporting, and is customizable. However, ad_form can be tricky to use. In addition to this document, the ad_form api documentation is helpful.

Multi-part Elements

Some elements have more than one choice, or can submit more than one value.

SELECT elements

  1. Creating the form element. Populate a list of lists with values for the option list.

    set foo_options [db_list_of_lists foo_option_list "
        select foo,
          from foos

    The variable foo_options should resemble {{first foo} 1234} {{second foo} 1235}

    Within ad_form, set up the element to use this list:

            {label "Which Foo"}
            {options $foo_options}

    This will result in a single name/value pair coming back in the submitted form. Handle this within the same ad_form structure, in the -new_data and -edit_data. In the example, it is available as $foo

See also the W3C spec for "The SELECT, OPTGROUP, and OPTION elements".

Using refreshes to pull additional information from the database

A situation you may run into often is where you want to pull in form items from a sub-category when the first category is selected. Ad_form makes this fairly easy to do. In the definition of your form element, include an HTML section

        {label "Subject"}
        {options {$task_options}}
        {html {onChange "document.form_name.__refreshing_p.value='1';submit()"}}
        {value $pm_task_id}

What this will do is set the value for pm_task_id and all the other form elements, and resubmit the form. If you then include a block that extends the form, you'll have the opportunity to add in subcategories:

    if {[info exists pm_task_id] && $pm_task_id ne ""} {
    db_1row get_task_values { }
    ad_form -extend -name form_name -form { ... }

Note that you will get strange results when you try to set the values for the form. You'll need to set them explicitly in an -on_refresh section of your ad_form. In that section, you'll get the values from the database, and set the values as so:

    db_1row get_task_values { }
    template::element set_value form_name estimated_hours_work $estimated_hours_work


A good way to troubleshoot when you're using ad_form is to add the following code at the top of the .tcl page (thanks Jerry Asher):

ns_log notice it's my page!
set mypage [ns_getform]
if {$mypage eq ""} {
    ns_log notice no form was submitted on my page
} else {
    ns_log notice the following form was submitted on my page
    ns_set print $mypage

Tips for form widgets

Here are some tips for dealing with some of the form widgets:

Current widget

Common Errors

Here are some common errors and what to do when you encounter them:

Error when selecting values

This generally happens when there is an error in your query.