RepeatingFieldSet Tips

The code in this article is abstracted from my working code, but I don’t have time to test this version (which is not 100% complete, as you will see). Since it took me a while to figure this out and I didn’t find any docs on it I thought I’d at least put down what I learned to give the next person a leg up on figuring it out.

My goal was to create an edit page for an SQLObject, where I wanted a list of sub-objects to be edited along with the main object. RepeatingFieldSet turned out to be perfect for this.

So suppose you have a model like:

class Foo(SQLObject):
    name = UnicodeCol()
    bars = RelatedJoin('Bar')

class Bar(SQLObject):
    name = UnicodeCol()
    description = UnicodeCol()

We can edit a Foo and all its Bars in one go with the following set of widgets:

form = TableForm(fields=[
    TextField(name='name',label='Name'),
    RepeatingFieldSet(
        name='bars',
        label='Bars',
        fields=[
            TextField(name='name',label='Name'),
            TextField(name='description', label='Description')
        ]
    )

Note that the name of the RepeatingFieldSet is bars, which means it will pick up its list of values from the ‘bars’ field of our Foo. Automagic niceness.

Here’s the controller:

@expose('.templates.editform')
def edit(self, tg_errors=None, **data):
    if tg_errors: flash("Fix your errors and resubmit")
    else: data = self.foo
    return dict(
        form=form,
        data=data,
        parms=dict(
            action=url('save'),
            submit_text="save",
            repetitions=dict(bars=len(self.foo.bars)+1)
        )
    )

This gives us one repeat of the fieldset for each Bar in Foo, and one more besides (so the user can add a new bar in the same form).

The callout for the form in editform.kid looks like this:

${form.display(data, **parms)}

The trickiest bit to figure out was how to modify the template for the RepeatingFieldSet widget. I didn’t actually want a repeating FieldSet, what I wanted was a table. This is what I came up with:

<div xmlns:py="http://purl.org/kid/ns#">
<table>
  <tr>
      <th py:for="field in fields">
        <label class="fieldlabel" for="${field.field_id}" py:content="field.label" />
      </th>
  </tr>
  <tr py:for="repetition in repetitions" class="${field_class}" id="${field_id}_${repetition}">
    <legend py:if="legend" py:content="legend" />
    <div py:for="field in hidden_fields"
        py:replace="field.display(value_for(field), **params_for(field))"
    />
    <td py:for="field in fields">
        <span py:content="field.display(value_for(field), **params_for(field))" />
        <span py:if="error_for(field)" class="fielderror" py:content="error_for(field)" />
    </td>
  </tr>
</table>
</div>

The ‘repetition in repetitions’ does some black mojo behind the scenes so that when we have reached repetition N in the loop, the various functions of each ‘field’ in ‘fields’ will pull data from the Nth element of the list of bars. But fields is just the widget list of the RepeatingFieldSet, so we can access the attributes of the widgets that do not relate to values, such as the label, at any point. That enables us to set the titles for the table columns before starting the values loop.