How can I find out the difference between when user changes fields and when field fills automatically from record on the table in onchange function?

Question

I have a many2one field as A and one2many field as A_details that A_details has filter base on A,

A = fields.Many2one(comodel_name="headertable")
A_details = fields.One2many(comodel_name="detailtable")
              

and in the xml I pass the A value with context in A_detail to filter it

<field name="A_detail" context="{'parent_id': A,}"/>

now I want to delete A_detail's records when user changes the A value, so I use onchange decorator on A field like this:

@api.onchange('A')
def _delete_selected_records(self):
    for rec in self.A_details:
            self.A_details = [(3, rec.id, 0)]    

this function workes correctly to create mode but the problem occurs when I open the record from tree view and while A field is getting value from model Onchanged decorator call the _delete_selected_records function and it delete all the A_detail's records, That's why I want to check in this function that if user change the A, delete the A_detail's records else if system sets value to field do nothing... how can I handle this???

Answer 1

You should add a check if A is deleted or not meaning if A is False then do X:

    @api.onchange('A')
    def _delete_selected_records(self):
        for rec in self:
           if rec.A is False:
              rec.A_details = [(3, rec.id, 0)] # You can you .unlink() btw
           else:
              continue 

This way even if the function is triggered by let's say a user accidentally putting cursor on the field in the view or something you won't risk deleting anything unless the correct condition is met.