How to Use write() Method on a Many2many Field in Odoo

The write() method in Odoo is used to update the values of records in a model. When working with a many2many field, the write() method can be used to add, remove, or replace the associated records in that field.

How to Use the write() Method on a many2many Field

A many2many field represents a bi-directional relationship between two models where multiple records of one model can be associated with multiple records of another model. The write() method on a many2many field takes specific commands to manage these relationships. The commands used to manipulate many2many fields are:

1. Add ((4, id)): Adds a record with a specific ID to the many2many field.
2. Remove ((3, id)): Removes a record with a specific ID from the many2many field.
3. Replace ((6, 0, [id1, id2, ...])): Replaces all existing records in the many2many field with the list of IDs provided.
4. Clear ((5, )): Clears all records from the many2many field.
5. Create and Link ((0, 0, {vals})): Creates a new record with the values provided and links it to the many2many field.

Practical Examples

Let’s assume we have the following models:

• Book Model (library.book)
• Author Model (library.author)

The library.book model has a many2many field named author_ids that links to the library.author model.

class LibraryBook(models.Model):
    _name = 'library.book'
    _description = 'Book Record'

    name = fields.Char(string='Title', required=True)
    author_ids = fields.Many2many('library.author', string='Authors')

Now, let’s see how to use the write() method to modify the many2many field author_ids:

1. Adding an Author to a Book

To add an existing author to a book, you can use the (4, id) command:

# Find the book and author records
book = self.env['library.book'].browse(book_id)
author_id = 5  # Example author ID to be added

# Add the author to the book's author_ids field
book.write({'author_ids': [(4, author_id)]})

2. Removing an Author from a Book

To remove an author from a book, you can use the (3, id) command:

# Find the book record
book = self.env['library.book'].browse(book_id)
author_id = 5  # Example author ID to be removed

# Remove the author from the book's author_ids field
book.write({'author_ids': [(3, author_id)]})

3. Replacing All Authors for a Book

To replace all existing authors with a new list of authors, use the (6, 0, [id1, id2, ...]) command:

# Find the book record
book = self.env['library.book'].browse(book_id)
new_author_ids = [1, 2, 3]  # New list of author IDs

# Replace all existing authors with the new list
book.write({'author_ids': [(6, 0, new_author_ids)]})

4. Clearing All Authors from a Book

To remove all authors associated with a book, use the (5,) command:

# Find the book record
book = self.env['library.book'].browse(book_id)

# Clear all authors from the book's author_ids field
book.write({'author_ids': [(5,)]})

5. Creating a New Author and Linking It to a Book

To create a new author and directly link it to a book, use the (0, 0, {vals}) command:

# Find the book record
book = self.env['library.book'].browse(book_id)
new_author_data = {'name': 'New Author Name'}  # Data for the new author

# Create a new author and link it to the book
book.write({'author_ids': [(0, 0, new_author_data)]})

Conclusion

The simple write() method in managed Odoo server solutions is utilized to update the values of previous records in any model. At the time of working with a many2many field, this method can be specially used to add, delete, or replace the related records in that specific field.