Odoo computed fields: works without store=True, doesn't work with store=True

Question

I have a computed field in Odoo with a function. Everything works fine when I don't add the store argument. When I add the store argument, it doesn't execute the code at all.

My code:

class opc_actuelewaardentags(models.Model):
    _name = 'opc_actuelewaardentags'

    unit = fields.Char(compute='changeunit')

    def changeunit(self):
        print "print"
        allrecords_actwaardent = self.search([])

        obj_taginst = self.env['opc_taginstellingen']
        allrecords_taginst = obj_taginst.search([])


        for i in allrecords_actwaardent:
            for j in allrecords_taginst:
                if i.tagnaam == j.tagnaam and i.unit != j.unit:
                    i.unit = j.unit

So: when I call the code like this:

unit = fields.Char(compute='changeunit')

The code is executed (shows "print").

When I call the code like this:

unit = fields.Char(compute='changeunit', store=True)

The code is not executed (doesn't show "print").

Is there anything wrong in my code? Or is this a bug? It seems so strange to me...

I need to be able to store the values in the database so I can filter on unit in the tree view.

edit: I applied Juan Salcedo's tip. Didn't work...

This is how I did it:

unit = fields.Char(default = changeunit)    

def changeunit(self):
    print "print"
    allrecords_actwaardent = self.search([])

    obj_taginst = self.env['opc_taginstellingen']
    #Hier dan i.p.v. self werken met dat obj_taginst
    allrecords_taginst = obj_taginst.search([])


for i in allrecords_actwaardent:
    for j in allrecords_taginst:
        if i.tagnaam == j.tagnaam and i.unit != j.unit:
            i.unit = j.unit
return i.unit

Gives error:

NameError: name 'changeunit' is not defined

I also tried putting the unit field below def changeunit(self), but didn't work either.

Answer 1

Store=True without @api.depends means it will execute only once while the column/field is going to be created.

so the effect you want to fire that method everytime will not be achieve with store=True without @api.depends or you need to remove store=True then it will calculate everytime when you access this field.

This are the changes you required to update in your code but before that you need to remove that column from database and after that restart server and upgrade module then it will come to there.

class opc_actuelewaardentags(models.Model):
    _name = 'opc_actuelewaardentags'

    unit = fields.Char(compute='changeunit')

    @api.multi
    def changeunit(self):
      print "print"  
        for obj in self:
            allrecords_actwaardent = self.search([])
            obj_taginst = self.env['opc_taginstellingen']
            allrecords_taginst = obj_taginst.search([])
            for i in allrecords_actwaardent:
                for j in allrecords_taginst:
                    if i.tagnaam == j.tagnaam and i.unit != j.unit:
                       obj.unit = j.unit
                       break

Another way: store = False never stored any value in database so if you want to store that value in database and don't won't to be updated (means it's fixed when create or update record) then you just need to override create/write method and inside update this field's value.

@api.model
def create(self, vals):
    vals.update({'field':value})
    return super(class_name,self).create(vals)