Hi,

You don't need api.onchange for date alone. You can do it in your button action as below,

@api.multi

def action_draft(self):

    for each in self:

        each.state = 'draft'

        each.draft_date = fields.Date.context_today(self)

    return True

I have an action button that calls the following function in python:

def action_draft(self):

    self.state = 'draft'

and want to set draft_date once the state is set as draft. like this:

@api.onchange('state')

def _onchange_state(self):

    if self.state == 'draft':

        self.draft_date = fields.Date.today()