Hi,

Please refer to the code:

from odoo import models, fields, api

class YourModel(models.Model):

    _name = 'your.model'

    account_id = fields.Many2one(

        'account.account',

        string='Fixed Asset Account',

        help="Select the fixed asset account."

    )

    capacity_form = fields.Selection(

        selection=lambda self: self._get_capacity_selection(),

        string='Capacity',

        help="Select the capacity for the selected fixed asset account."

    )

    @api.model

    def _get_capacity_selection(self):

        # Default empty if no context

        account_id = self.env.context.get('default_account_id')

        if not account_id:

            return []

        asset_records = self.env['account.asset'].search([

            ('account_asset_id', '=', account_id)

        ])

        return [(asset.capacity, asset.capacity) for asset in asset_records if asset.capacity]

Since selection fields are static per field definition, the usual trick is to use a Many2one instead of a Selection. You can then dynamically restrict values with a domain:

from odoo import models, fields, api

class YourModel(models.Model):

    _name = 'your.model'

    account_id = fields.Many2one(

        'account.account',

        string='Fixed Asset Account',

        help="Select the fixed asset account."

    )

    capacity_form_ids = fields.Many2many(

        'account.asset',

        compute='_compute_capacity_form_ids',

        string='Available Capacities'

    )

    capacity_form_id = fields.Many2one(

        'account.asset',

        string='Capacity',

        domain="[('id', 'in', capacity_form_ids)]"

    )

    @api.depends('account_id')

    def _compute_capacity_form_ids(self):

        for rec in self:

            if rec.account_id:

                assets = self.env['account.asset'].search([

                    ('account_asset_id', '=', rec.account_id.id),

                    ('capacity', '!=', False)

                ])

                rec.capacity_form_ids = assets

            else:

                rec.capacity_form_ids = False

Hope it helps.

Following is the code @Ray Carnes

account_id = fields.Many2one(
    'account.account',
    string='Fixed Asset Account',
    help="Select the fixed asset account."
)
capacity_form = fields.Selection(
    selection=[],
    string='Capacity',
    help="Select the capacity for the selected fixed asset account."
)

@api.onchange('account_id')
def _onchange_account_id(self):
    if self.account_id:
        # Fetch all capacities related to the selected account
        asset_records = self.env['account.asset'].search([
            ('account_asset_id', '=', self.account_id.id)
        ])
        # Prepare the selection list
        capacities = [(asset.capacity, asset.capacity) for asset in asset_records if asset.capacity]
        print('Capacities are', capacities)

        # Dynamically update the selection options for capacity_form
        self._fields['capacity_form'].selection = capacities
        self.capacity_form = capacities

        # Reset the value of capacity_form if it doesn't match the new options
        if self.capacity_form not in dict(capacities):
            self.capacity_form = False
    else:
        # Clear the selection if no account_id is selected
        self._fields['capacity_form'].selection = []
        self.capacity_form = False