Odoo, as a highly customizable ERP system, offers numerous ways to automate and enhance business processes. One of the essential mechanisms for customization is the use of computed fields, which calculate values dynamically based on other fields in the model. However, by default, computed fields in Odoo are read-only. If you want to allow users to modify a computed field and have those changes reflected in other dependent fields, you can achieve this by defining an inverse function.
This blog explores how to add an inverse function for computed fields in Odoo 18, covering its usage, importance, and implementation. We will also walk through an example to demonstrate its practical application.
What are Computed Fields?
A computed field is a field whose value is computed dynamically by the system based on other fields. These fields are not directly stored in the database but are calculated on the fly using a function defined in the model. Computed fields are useful when the value of the field is dependent on the value of other fields or requires some logical calculation.
Defining a Computed Field
To define a computed field in Odoo, you use the compute argument in the field definition. For example:
class ExampleModel(models.Model):
_name = 'example.model'
total = fields.Float(compute='_compute_total')
@api.depends('line_ids.price', 'line_ids.quantity')
def _compute_total(self):
for record in self:
record.total = sum(line.price * line.quantity for line in record.line_ids)
Here, the 'total' field is computed using the '_compute_total' method. The method sums the product of 'price' and 'quantity' from related lines ('line_ids'). The '@api.depends' decorator ensures that the 'total' is recalculated whenever 'price' or 'quantity' changes.
Limitation of Computed Fields
By default, computed fields are read-only, meaning that users cannot directly modify them in the user interface (UI). This is because their values are automatically generated by Odoo based on other fields. While computed fields are helpful for automating calculations, there are cases when you may want users to edit these fields manually and still have the logic adjust other fields accordingly.
For example, imagine a computed field that calculates a total price. If a user changes this total price manually, you may want the unit prices or quantities of the related items to be adjusted automatically. This is where the inverse function comes into play.
What is an Inverse Function?
An inverse function allows a computed field to be editable by defining how the field’s value will affect other fields in the model. In other words, the inverse function tells Odoo how to update other fields when a computed field is manually changed by a user. With an inverse function, computed fields can become bidirectional—Odoo can both calculate their values and update dependent fields when the computed field is changed.
Inverse Function Syntax
Here’s the general syntax for adding an inverse function to a computed field:
class ExampleModel(models.Model):
_name = 'example.model'
total = fields.Float(compute='_compute_total',
inverse='_inverse_total')
@api.depends('line_ids.price', 'line_ids.quantity')
def _compute_total(self):
for record in self:
record.total = sum(line.price * line.quantity for line in
record.line_ids)
def _inverse_total(self):
for record in self:
# Logic to update the dependent fields when total is
# manually edited
total_quantity = sum(line.quantity for line in
record.line_ids)
if total_quantity:
for line in record.line_ids:
line.price = record.total / total_quantity
In this example, the 'total' field is calculated using the '_compute_total' method, and the '_inverse_total' function updates the prices of the related lines when 'total' is modified by the user.
Components of the Inverse Function
* compute='_compute_total': This argument defines the function used to calculate the value of the field.
* inverse='_inverse_total': This argument defines the function to update the related fields when the computed field (total) is manually changed.
The inverse function allows you to maintain consistency between fields by adjusting related fields based on the new value of the computed field.
Conclusion
Computed fields in Odoo are incredibly useful for automating calculations and displaying dynamic values. However, when you need to allow users to manually adjust these fields, an inverse function becomes essential. It provides a way to control how computed fields are updated and how those updates affect other related fields.
In Odoo 18, adding an inverse function allows you to make computed fields editable while ensuring that changes propagate to other fields logically. By following the steps outlined in this blog, you can implement this feature effectively in your Odoo customizations and enhance the overall flexibility of your models.