Get the current company without ids or uid in Odoo / OpenERP
Not sure I completely understand your question.
A user may be able to do something in any company depending on their list of allowed companies, but a user can only ever do something in one company at a time.
Any user can change their current company to one of the companies they are allowed but when they do this, the company_id on the user record is changed so if you browse res.users using the UID you will always get the current company of the user.
The only exception I can think of is if you give the user a list of companies they are allowed to see and give them a button or check box to do something on that company.  In this case, your screen will need to be backed by a model and you can check on there so see which company they chose, either by browsing to see which record has the checkbox set, or if you put a button or action on a tree view, the method will get the IDs of the records selected.
I need to create a function that takes a default value, this value is distinct for each company.
Thing is that I can't use the uid because the user can do this in any company, and I have no object to ask ids for because its for a default field.
Is there any way to get the current company without using ids or the uid ?
Thanks in advance.