[Django]-How to put a value from request.GET as a hidden input in django-crispy-forms

Finally, I figured it out by myself.

To solve this problem, the context_data in the original template based solution should be passed as initial into the constructor of forms.Form.

For example, with django CVB, get_initial is the right point to pass initial data to forms

def get_initial(self):
  initial = Super(ThisCBV, self).get_initial()
  redirect_field_name = self.get_redirect_field_name()
  if (redirect_field_name in self.request.GET and 
      redirect_field_value in self.request.GET):
      initial.update({
           "redirect_field_name": redirect_field_name,
           "redirect_field_value": self.request.REQUEST.get(
               redirect_field_name),
      })
  return initial

Then, it is possible to add a field dynamically in the instance of forms.Form

def __init__(self, *args, **kwargs):
  super(ThisForm, self).__init__(*args, **kwargs)
  if ('redirect_field_name' in kwargs['initial'] and
      'redirect_field_value' in kwargs['initial']):

      self.has_redirection = True
      self.redirect_field_name = kwargs['initial'].get('redirect_field_name')
      self.redirect_field_value = kwargs['initial'].get('redirect_field_value')

      ## dynamically add a field into form
      hidden_field = forms.CharField(widget=forms.HiddenInput())
      self.fields.update({
        self.redirect_field_name: hidden_field
      })

  ## show this field in layout
  self.helper = FormHelper()
  self.helper.layout = Layout(
    Field(
      self.redirect_field_name,
      type='hidden',
      value=self.redirect_field_value
    )
  )

You can ask Django Crispy Form to not render the <form> tag, and only generate the <input> tags, which will let you then add your own extra <input>.

You do this by setting the form helper’s form_tag property to False.

This is all documented in detail here. Note that unlike the example, you won’t need {% crispy second_form %}, you’ll only need to add your own if block there.