set the css class of a form widget based on the data

[Michael]

Hi,

The ``attrs`` attribute of a widget allows to define the html attributes. For example, setting it to ``widget.attrs['class'] = 'class1 class2'`` will add ``class="class1 class2"`` on the rendered widget.

However, how can I set them based on the data? I display an update form and I'd like to change the CSS class based on the data that is going to be displayed when the form is rendered.

Where could I check for the data in order to change the ``attrs`` property of the widget before it is rendered?

Thanks

[Russell Keith-Magee]

Hi Michael,

The best bet would be to write a custom widget, and override the render() method. render() takes the name of the widget, the value to render, and a dictionary of attr values. In your subclass, you can override this method to inject the additional attributes based on the provided value - something like:

class MyWidget(TextInput):

    def render(self, name, value, attrs=None):

        if value == SPECIAL VALUE:

            attrs['class'] = 'class1 class2'

        return super(MyWidget, self).render(name, value, attrs)

This is an oversimplification - there's a few extra edge cases you'll need to account for - if attrs is none, or if 'class' already exists - but the idea should hopefully make sense.

Yours,

Russ Magee %-)

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[Michael Palumbo]

Thanks Russell, that works well.

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