API in Odoo

1.@api.returns

It will return a RecordSet of specified model based on original returned value:

@api.returns('res.partner')

def afun(self):

.

.

.

return x # a RecordSet

2.@api.one

The decorated method automatically loops on records (i.e, for each record in recordset it calls the method), and makes a list with the results.

self is redefined as current record:

@api.one

def afun(self):

self.name='todo'

3.@api.multi

The method typically defines an operation on records. Such a method:

Self will be the current RecordSet without iteration.

@api.multi

def afun(self):

len(self)

4.@api.model

This decorator will convert old API calls to decorated function to new API signature.

@api.model

def afun(self):

pass

5.@api.constrains

This decorator will ensure that decorated function will be called on create, write, unlink operation. If a constraint is met the function should raise a

openerp.exceptions.Warning with appropriate message.

6.@api.depends

This decorator will trigger the call to the decorated function if any of the fields specified in the decorator is altered by ORM or changed in the form:

@api.depends('name', 'an_other_field')

def afun(self):

pass

1. 7.@api.onchange

This decorator will trigger the call to the decorated function if any of the fields specified in the decorator is changed in the form:

@api.onchange('fieldx')

def do_stuff(self):

if self.fieldx == x:

self.fieldy = 'toto'

In previous sample self corresponds to the record currently edited on the form. When in on_change context all work is done in the cache. So you can alter RecordSet inside your function without being worried about altering database. That’s the main difference with @api.depends

At function return, differences between the cache and the RecordSet will be returned to the form.

2. 8.@api.noguess

This decorator prevent new API decorators to alter the output of a method

Source : http://zbeanztech.com/blog/method-decorators-odoo-8  
              http://odoo-new-api-guide-line.readthedocs.io/en/latest/decorator.html