How to Implement @onchange vs @compute with inverse in Odoo? | Vraja Technologies

How to Implement @onchange vs @compute with inverse in Odoo?

✅ Purpose & Concept

Feature	@onchange	@compute (with @inverse)
Triggered When	Field changes in UI (form view only)	Any relevant field changes in DB (backend + UI)
Stores Value?	No (unless explicitly written)	Yes (if store=True)
Bidirectional?	One-way (UI to logic)	Yes (both compute and inverse)
Runs In	Client side	Server side (always)
Used In Views?	Yes	Yes

📌 Real Use Case: Set Discount Based on Product

@onchange Example

class SaleOrderLine(models.Model):

_inherit = 'sale.order.line'

@api.onchange('product_id')

def _onchange_product_id(self):

if self.product_id and self.product_id.list_price > 1000:

self.discount = 10

When you choose a product, if its price exceeds 1000, a 10% discount will be automatically applied.
Only works in form view during manual data entry.
Does not trigger in batch creation or server-side operations like imports, APIs.

@compute with @inverse Example

class SaleOrderLine(models.Model):

_inherit = 'sale.order.line'

price_tax = fields.Float(compute='_compute_price_tax', inverse='_inverse_price_tax', store=True)

@api.depends('price_unit', 'tax_id')

def _compute_price_tax(self):

for line in self:

tax = line.price_unit * 0.18 if line.tax_id else 0.0

line.price_tax = tax

def _inverse_price_tax(self):

for line in self:

if line.tax_id:

line.price_unit = line.price_tax / 0.18

Automatically calculates tax from price and stores it.
Also allows you to set the tax manually, and it will update price_unit accordingly using the inverse method.
Useful for data consistency, import/export, and automations.

⚙️ When to Use What?

Situation	Use @onchange	Use @compute + @inverse
Field logic only needed in UI	✅ Yes	❌ Not necessary
Field must be updated on record change	❌ No	✅ Yes
Bi-directional calculation needed	❌ No	✅ Yes (compute + inverse)
Works during create/update/import	❌ No	✅ Yes
Temporary field logic (not stored)	✅ Yes	❌ Only if compute is not stored

✅ Summary Table