Model Inheritance in Odoo: Single vs Multi-Table Inheritance Explained

class Student(models.Model):
    _name = 'student'
    
    name = fields.Char()  # DUPLICATE of res.partner.name
    email = fields.Char()  # DUPLICATE of res.partner.email
    phone = fields.Char()  # DUPLICATE of res.partner.phone
    enrollment_date = fields.Date()

class Student(models.Model):
    _name = 'student'
    _inherits = {'res.partner': 'partner_id'}
    
    partner_id = fields.Many2one('res.partner', required=True, ondelete='cascade')
    enrollment_date = fields.Date()
    course = fields.Char()
    grade = fields.Float()

class ResPartner(models.Model):
    _inherit = 'res.partner'  # Only _inherit, no _name
    
    loyalty_points = fields.Integer(string='Loyalty Points')
    preferred_payment = fields.Selection([
        ('credit_card', 'Credit Card'),
        ('paypal', 'PayPal'),
        ('bank_transfer', 'Bank Transfer'),
    ])

class ResPartner(models.Model):
    _inherit = 'res.partner'
    
    loyalty_tier = fields.Selection([
        ('bronze', 'Bronze'),
        ('silver', 'Silver'),
        ('gold', 'Gold'),
        ('platinum', 'Platinum'),
    ], default='bronze', string='Loyalty Tier')
    
    lifetime_value = fields.Float(
        string='Lifetime Purchase Value',
        compute='_compute_lifetime_value',
        store=True
    )
    
    total_orders = fields.Integer(
        string='Total Orders',
        compute='_compute_total_orders',
        store=True
    )
    
    @api.depends('order_ids')
    def _compute_lifetime_value(self):
        """Calculate total value of all orders from this customer."""
        for record in self:
            record.lifetime_value = sum(order.amount_total 
                                       for order in record.order_ids)
    
    @api.depends('order_ids')
    def _compute_total_orders(self):
        """Count total orders from this customer."""
        for record in self:
            record.total_orders = len(record.order_ids)

class Supplier(models.Model):
    _name = 'supplier'           # NEW model
    _inherit = 'res.partner'     # Inherits from res.partner
    
    supplier_code = fields.Char()
    lead_time_days = fields.Integer()

class Supplier(models.Model):
    _name = 'supplier'
    _inherit = 'res.partner'  # Supplier IS a partner
    
    supplier_code = fields.Char(string='Supplier Code', required=True)
    lead_time_days = fields.Integer(string='Lead Time (days)')
    minimum_order_qty = fields.Float(string='Min Order Qty')
    
    average_rating = fields.Float(
        string='Average Rating',
        compute='_compute_average_rating'
    )
    
    purchase_order_ids = fields.One2many(
        'purchase.order', 'supplier_id',
        string='Purchase Orders'
    )
    
    @api.depends('purchase_order_ids')
    def _compute_average_rating(self):
        """Calculate supplier rating from purchase order history."""
        for record in self:
            if record.purchase_order_ids:
                ratings = [po.supplier_rating for po in record.purchase_order_ids 
                          if po.supplier_rating]
                record.average_rating = sum(ratings) / len(ratings) if ratings else 0
            else:
                record.average_rating = 0

class Student(models.Model):
    _name = 'student'
    _inherits = {'res.partner': 'partner_id'}
    
    # REQUIRED: Many2one field linking to parent
    partner_id = fields.Many2one(
        'res.partner',
        required=True,
        ondelete='cascade',
        auto_join=True,
        index=True
    )
    
    # Custom fields for student
    enrollment_date = fields.Date()
    course_id = fields.Many2one('course')
    grade = fields.Float()

student = self.env['student'].create({
    'partner_id': 1000,  # Link to existing partner
    'enrollment_date': '2025-01-15',
    'course_id': 10,
})

# Access partner fields through delegation
print(student.name)          # Accesses partner_id.name (automatic delegation)
print(student.email)         # Accesses partner_id.email
print(student.enrollment_date)  # Direct field on student

class VendorAccount(models.Model):
    _name = 'vendor.account'
    _inherits = {'res.partner': 'partner_id'}
    
    partner_id = fields.Many2one(
        'res.partner',
        required=True,
        ondelete='cascade',
        auto_join=True,
        index=True
    )
    
    # Channel-specific fields
    shopify_id = fields.Char(string='Shopify Vendor ID')
    shopify_commission = fields.Float(string='Shopify Commission %')
    amazon_seller_id = fields.Char(string='Amazon Seller ID')
    amazon_commission = fields.Float(string='Amazon Commission %')
    stripe_account_id = fields.Char(string='Stripe Account ID')
    
    payment_method = fields.Selection([
        ('bank_transfer', 'Bank Transfer'),
        ('paypal', 'PayPal'),
        ('stripe', 'Stripe'),
    ])
    
    total_sales = fields.Float(
        string='Total Sales',
        compute='_compute_total_sales',
        store=True
    )

# Access vendor data
vendor = self.env['vendor.account'].search([('shopify_id', '=', '12345')])
print(vendor.name)              # From res.partner (delegated)
print(vendor.email)             # From res.partner (delegated)
print(vendor.shopify_commission) # Direct field

# Type 1: Extension Inheritance
# Add loyalty fields to existing res.partner
class ResPartner(models.Model):
    _inherit = 'res.partner'
    
    loyalty_points = fields.Integer(string='Loyalty Points')
    vip_customer = fields.Boolean(string='VIP Customer')

# Type 2: Classical Inheritance
# Create new Supplier model, inherits from res.partner
class Supplier(models.Model):
    _name = 'supplier'
    _inherit = 'res.partner'
    
    supplier_code = fields.Char()
    lead_time = fields.Integer()
    # Has access to res.partner fields (name, email, etc.)
    # Stored in separate supplier table

# Type 3: Delegation Inheritance
# Create new Affiliate model, delegates to res.partner
class Affiliate(models.Model):
    _name = 'affiliate'
    _inherits = {'res.partner': 'partner_id'}
    
    partner_id = fields.Many2one('res.partner', required=True, ondelete='cascade')
    affiliate_code = fields.Char()
    commission_rate = fields.Float()
    total_referral_sales = fields.Float(compute='_compute_referral_sales')