Example code for Many2one & One2many fields

example_model.py

from odoo import models, fields


class ParentModel(models.Model):
    _name = 'parent.model'
    
    parent_field_1 = fields.Char(string="Parent Field 1")
    parent_field_2 = fields.Integer(string="Parent Field 2")
    
    # If you want to display child data, you must create One2many field.
    # The One2many field used for inverse field from Many2one field
    child_field_ids = fields.One2many('child.model', 'parent_field_id', string="Child IDS")


class ChildModel(models.Model):
    _name = 'child.model'
    
    child_field_1 = fields.Char(string="Child Field 1")
    child_field_2 = fields.Integer(string="Child Field 2")
    child_field_3 = fields.Boolean(string="Child Field 3")
    parent_field_id = fields.Many2one('parent.model', string="Parent ID")

example_view.xml

<odoo>
    <record model="ir.ui.view" id="view_parent_form">
        <field name="name">parent.model.form</field>
        <field name="model">parent.model</field>
        <field name="arch" type="xml">
            <form>
                <sheet>
                    <group>
                        <field name="parent_field_1"/>
                        <field name="parent_field_2"/>
                    </group>
                    <notebook>
                        <page string="Child Data">
                            <!-- you can display child data like code below -->
                            <field name="child_field_ids">
                                <tree>
                                    <field name="child_field_1"/>
                                    <field name="child_field_2"/>
                                    <field name="child_field_3"/>
                                </tree>
                            </field>
                        </page>
                    </notebook>
                </sheet>
            </form>
        </field>
    </record>
</odoo>

why you display "child" in dropdown? "child" should display in tree view because "parent" is One2many to "child". It means one "parent" have many "child", right?
so if you choose some "parent" it will display all "child" automatically on parent form.

from your image, i think you want to use 3 model, right? Parent -> Many2one -> Child -> One2many -> GrandChild

OK, let's imagine that we want to choose Parent, so that shows us the list of the children in our tree. and that's what I want.

I already understand the relationship
my goal and populate the tree automatically

Hey @Gelson15 . Were you able to find a way to automatically populate a One2many tree view?

I am also looking for a similar solution, If anyone has found an answer to this please share

in my project I have the same relation and it's working fine
but when I delete the child record from the parent tree view (for example) it's being deleted from the database :(