Dear Mohamed,

Try to use Related Field Related Field Link

Hoping to Solve the issue,

You can Use Onchange Function :

married is Many2one with same model:

@api.onchange('married')

def onchange_married(self):

    self.married.married= self.id

Try it

Dear Boubaker and Aymen

I don't think that related field will solve my problem because what i am looking for is not how to get the field of the other record.

I want when i link the record A with record B, record B will be linked with A.
A.married_with(B)   ====>   B.married_with(A)
I hope that my problem is clear

Hi Mohamed Ali 

When you change for example   the customer, you want to change it with another field

1- You can link it to Related

for example 

    partner_id = fields.Many2one('res.parner', string="Partner")
    phone = fields.Char( string="Phone", related='partner_id .phone')

phone This field is present in the model 'res.parner' 

2- the other solution by Methode On_change 

@api.onchange('partner_id')
def on_change_field(self):
    self.phone = self.partner_id.phone