Hello medmars,

For example , If you want to put attachment button inside a form then you should follow below steps:

Python code :

class Employee(models.Model):
   
_inherit = "hr.employee"
   
_description = "Employee"
 
   
doc_count = fields.Integer(compute='_compute_attached_docs_count',
string="Number of documents attached")
    
    def
attachment_tree_view(self):
       
domain = ['&', ('res_model', '=', 'hr.employee'), ('res_id', 'in',
self.ids)]
       
res_id = self.ids and self.ids[0] or False
       
return {
           
'name': _('Attachments'),
           
'domain': domain,
           
'res_model': 'ir.attachment',
           
'type': 'ir.actions.act_window',
           
'view_id': False,
           
'view_mode': 'kanban,tree,form',
           
'view_type': 'form',
           
'help': _('''<p class="oe_view_nocontent_create">
           
                                    Attach
documents of your employee.</p>'''),
           
'limit': 80,
           
'context': "{'default_res_model': '%s','default_res_id': %d}"
% (self._name, res_id)
       
}
 
    def _compute_attached_docs_count(self):
       
Attachment = self.env['ir.attachment']
       
for employee in self:
           
employee.doc_count = Attachment.search_count([('res_model', '=',
'hr.employee'), ('res_id', '=', employee.id)])

XML Code:

<?xml version="1.0"
encoding="utf-8"?>
<odoo>
   
<data>
       
<record id="view_employee_documents_form"
model="ir.ui.view">
           
<field
name="name">hr.employee.documents.form</field>
           
<field name="model">hr.employee</field>
           
<field name="inherit_id"
ref="hr.view_employee_form"/>
           
<field name="arch" type="xml">
               
<xpath expr="//button[@name='toggle_active']"
position="before">
                    <button  class="oe_stat_button"
name="attachment_tree_view" 
type="object" icon="fa-files-o">
                        <field
string="Documents" name="doc_count"
widget="statinfo"/>
                    </button>
               
</xpath>
           
</field>
       
</record>
   
</data>
</odoo>

Output :

You can see attachment button in view as below :