Chapter 3 - Odoo 15 Development Book

Inheritance

In any module customization, there are some situations where we need to inherit some models in order to achieve our business requirements. For extending an existing model, we can use _inherit attributes. Odoo provides two inheritance mechanisms to extend an existing model in a modular way.

Classical Inheritance:

The classic inheritance where we use both _name and _inherit attributes together. In addition, the new models get all methods, fields from its base.

For example:Parent model

class ParentModel(models.Model):
   _name = 'parent.model'
   name = fields.Char()

Child Model

class ChildModel(models.Model):
   _name = 'child.model'
   _inherit = 'parent.model'
   date = fields.Date()

Here we can access all functionality of parent model from the child model.

Prototype Inheritance:

When we want to add a new field or add a method to an existing model, we can use this inheritance. In this type inheritance, we will only use _inherit attribute. The child model is replaced with the new existing one.

For example:Parent model

class ParentModel(models.Model):
   _name = 'parent.model'
   name = fields.Char()

Child Model

class InheritModel(models.Model):
   _inherit = 'parent.model'
   Text = fields.Char()

When we check the database we can see the newly created fields are added to the model. And also possible to create and override the methods.

Delegation Inheritance:

When we want to sink another model to your current model without affecting the views, we can use delegation inheritance. In this type inheritance, we use the _inherits attribute.

For example:

class ProductTemplate(models.Model):
  _name = "product.template"
class ProductProduct(models.Model):
  _name = "product.product"
  _inherits = {'product.template': 'product_tmpl_id'}
  Product_tmpl_id = fields.Many2one('product.template', 'Product Template', auto_join=True, index=True, ondelete="cascade", required=True)

View Inheritance:

When we need to overwrite an existing view, we can use view inheritance. These extensions can both add and remove content from their parent view. By using inherit_id field, we can extend the existing view.

For example:

<record id="inherited_model_view_form" model="ir.ui.view">
       <field name="name">inherited.product.form.inherit.test</field>
       <field name="model">product.template</field>
       <field name="inherit_id" ref="product.product_template_form_view"/>
       <field name="arch" type="xml">
           <xpath expr="//field[@name=name]" position="after">
               <field name="new_field"/>
           </xpath>
       </field>
   </record>

expr: expression for selecting the single elements in parent view Position: Operation to apply the matched elements, some of the operations are after, before, inside, attributes.