Question

I have two functional fields in OpenERP that are not stored in the db. In fact, they don’t have columns in the db. They are calculate on the fly from other tables. I want to be able to calculate their sum or difference. I saw something here (calculate sum of fields) that does that but I think it goes to the db to fetch the data. Please how can I achieve this. Is the best option to store the data in the db and pull it from there?

Answer 1

Their can be alternate solution like, define third calculation field and use the “multi=”” and also calculate the difference and either you can save that third field in db or you can keep it dynamic if you need for later external usage.

Advantage over here will be after calculation your 2 field store diff for the third field.

Example Code Snippet is as Follow :

class code_play(osv.osv):
_name = 'code.play'

def _calc_function(self, cr, uid, ids, fields_list, args, context=None):
    vals = {}
    for id in ids:
        fields = {}
        for field in fields_list:
            fields[field] = 10
        fields["calc3"] = fields['calc1'] + fields['calc2']
        vals[id] = fields
    return vals       

_columns = {
    'name': fields.char('Name', required=True, size=50),
    'calc1': fields.function(_calc_function, type='integer', store=False, multi="compute_person_data"),
    'calc2': fields.function(_calc_function, type='integer', store=False, multi="compute_person_data"),
    'calc3': fields.function(_calc_function, type='integer', store=False, multi="compute_person_data"),
}

As i explained up again field with multi will be calculated but same function so return type will be

    # when called with ``ids=[1,2,3]``, ``compute_person_data`` could return:
    {
        1: {'calc1': 10, 'calc2': 10, 'calc3': 20},
        2: {'calc1': 10, 'calc2': 10, 'calc3': 20},
        3: {'calc1': 10, 'calc2': 10, 'calc3': 20}
    }

Regards