Question

I’m wondering how to change the behavior of a form field based on data in the request… especially as it relates to the Django Admin. For example, I’d like to decrypt a field in the admin based on request data (such as POST or session variables).

My thoughts are to start looking at overriding the change_view method in django/contrib/admin/options.py, since that has access to the request. However, I’m not sure how to affect how the field value displays the field depending on some value in the request. If the request has the correct value, the field value would be displayed; otherwise, the field value would return something like “NA”.

My thought is that if I could somehow get that request value into the to_python() method, I could directly impact how the field is displayed. Should I try passing the request value into the form init and then somehow into the field init? Any suggestions how I might approach this?

Thanks for reading.

In models.py

class MyModel(models.Model):
    hidden_data = models.CharField()

In admin.py

class MyModelAdmin(models.ModelAdmin):
    class Meta: 
        model = MyModel

def change_view(self, request, object_id, extra_context=None):
    .... # Perhaps this is where I'd do a lot of overriding? 
    ....
    return self.render_change_form(request, context, change=True, obj=obj)

Answer 1

I haven’t tested this, but you could just overwrite the render_change_form method of the ModelAdmin to sneak in your code to change the field value between when the change_view is processed and the actual template rendered

class MyModelAdmin(admin.ModelAdmin):
    ...
    def render_change_form(self, request, context, **kwargs):
        # Here we have access to the request, the object being displayed and the context which contains the form
        form = content['adminform'].form
        field = form.fields['field_name']
        ...
        if 'obj' in kwargs:
            # Existing obj is being saved
        else:
            # New object is being created (an empty form)
        return super(MyModelAdmin).render_change_form(request, context, **kwargs)