Hi, 

I am developing an app for testing purpose. In this app I need to copy records saved in one model (includes One2many field aswell) to other model by clicking a button that calls the function which is programmed to the stated task. (Same as Quotation ===> Invoice in sales module)

Here is my model

ORIGIN MODEL (Source, Records will be entered via this model)

from odoo import models, fields, api
from datetime import datetime

class cms_project(models.Model):
    _name = 'cms.project'
    _description = 'Projects'
    _order = 'name asc'  # asc or desc

    name = fields.Char(string="Project ID", required=True, readonly=True, copy=False, index=True, default='New')
    project_short = fields.Char(string="Short Name of Project", required=True)
    project_desc = fields.Text(string="Full Name of Work", required=True)
    client = fields.Many2one('cms.client', 'Client')  # Get Client List from cms.client model
    project_ecv = fields.Monetary(compute='_compute_ecv', string="Estimated Cost of Project", readonly=True, store=True)
    rebate = fields.Float(string="Percentage (+/-)", required=True)
    quoted_total = fields.Monetary(string='Quoted Cost Value of the Work', store=True, readonly=True,
                                   compute='_quoted_total')

    work_order_number = fields.Char(string="Client Work Order No.")
    work_order_date = fields.Date(string='Work Order Date', required=True, index=True, default=datetime.today())
    completion_date = fields.Date(string='Estimated Completition Date', required=True, index=True,
                                  default=datetime.today())

    completion_time = fields.Integer(compute='_compute_completion_time', string="Completion time (in Days)",
                                     required=True, index=True, store=False)
    remaining_completition_days = fields.Integer(compute='_compute_remaining_completition_days',
                                                 string="Remaining Completion Time (in Days)")
    currency_id = fields.Many2one(related='boq_line.currency_id', depends=['boq_line.currency_id'], store=True,
                                  string='Currency')
    boq_line = fields.One2many('cms.boq.lines', 'boq_id', string='BOQ Lines', copy=True, auto_join=True)
    note = fields.Text(string="Notes on BOQ")

    @api.model
    def create(self, vals):
        if vals.get('name', 'New') == 'New':
            vals['name'] = self.env['ir.sequence'].next_by_code(
                'project.id.seq') or 'New'
        return super(cms_project, self).create(vals)  # Use return command directly without any "RESULT"

    _sql_constraints = [
        ('pr_short_uniq',
         'UNIQUE (project_short)',
         'Short name already exists.'),
        ('pr_id_uniq',
         'UNIQUE (name)',
         'ID already exists.')]

    def _compute_completion_time(self):
        for record in self:
            record.completion_time = (record.completion_date - record.work_order_date).days

    def _compute_remaining_completition_days(self):
        for record in self:
            record.remaining_completition_days = (record.completion_date - fields.Date.today()).days

    @api.depends('boq_line.amount')
    def _compute_ecv(self):
        global order, ecv_total
        for order in self:
            ecv_total = 0.0
            for line in order.boq_line:
                ecv_total += line.amount
        order.update({'project_ecv': ecv_total})

    @api.depends('project_ecv', 'rebate')
    def _quoted_total(self):
        for order in self:
            calculated = order.project_ecv + (order.project_ecv * (order.rebate / 100))
            order.update({
                'quoted_total': calculated,
            })

    @api.model
    def create_mb(self,cr):

        mb_val_list = []
        for order in self:
            # prepare MB environment
            mb_vals = order._prepare_mb()
            # prepare MB lines
            for line in order.boq_line:
                #self.env['mb.entry.line'].create(line._prepare_mb_line())
                mb_vals['mb_line'].append((0, 0, line._prepare_mb_line()))
            mb_val_list.append(mb_vals)
        moves = self.env['mb.entry'].create(mb_val_list)
        return moves

    @api.model
    def _prepare_mb(self):
        self.ensure_one()
        mb_vals = {
            'mb_no': self.name,
            'project_short': self.project_short,
            'project_desc': self.project_desc,
            'project_ecv': self.project_desc,
            'client': self.client,
            'rebate': self.rebate,
            'quoted_total': self.quoted_total,
            'work_order_number': self.work_order_number,
            'work_order_date': self.work_order_date,
            'completion_date': self.completion_date,
            'completion_time': self.completion_time,
            'remaining_completition_days': self.remaining_completition_days,
            'currency_id': self.currency_id,
            'mb_line': [],
        }
        return mb_vals

class cms_boq_lines(models.Model):
    _name = 'cms.boq.lines'
    _description = "BOQ Lines"
    _rec_name = 'item_id'
    # name = fields.Char(string="BOQ Lines")
    boq_id = fields.Many2one('cms.project', string='BOQ ID', copy=True, required=True, ondelete='cascade', index=True)

    item_id = fields.Char(string="SNo.", store=True)
    item_short = fields.Many2one('product.product', string='Item', store=True)
    item_des = fields.Text(string='Item Description', store=True)
    item_qty = fields.Float(string="Estimated QTY.", required=True, digits=(30, 3), store=True)
    item_rate = fields.Monetary(string="SOR Rate", required=True, store=True, )
    uom = fields.Many2one('uom.uom', string='Per', store=True)
    amount = fields.Monetary(compute='_amount', readonly=True, string="Amount", required=True, strore=True)
    currency_id = fields.Many2one('res.currency', string='Currency')

    @api.depends('item_qty', 'item_rate')
    def _amount(self):
        for line in self:
            qty = line.item_qty
            rate = line.item_rate
            line.amount = qty * rate

    def _prepare_mb_line(self):
        self.ensure_one()
        res = {
            'boq_id': self.boq_id,
            'mb_id':self.boq_id,
            'item_id': self.item_id,
            'item_short': self.item_short,
            'item_qty': self.item_qty,
            'item_des': self.item_des,
            'item_rate': self.item_rate,
            'uom': self.uom,
            'amount': self.amount,
        }
        return res    

Destination MODEL ( Records will be replicated in this model)

from odoo import models, fields, api
from datetime import datetime

class mb_entry(models.Model):
    _name = 'mb.entry'
    _description = "Measurement Book"
    _rec_name = 'mb_no'
    mb_no = fields.Char(string="MB SNo.")

    execution_date = fields.Date(string='Execution Date', required=True, index=True, default=datetime.today())
    entry_date = fields.Date(string='Entry Date', required=True, index=True, default=datetime.today(), readonly=True)

    project = fields.Char(string='Project')
    project_short = fields.Char(string="Short Name of Project", required=True)
    project_desc = fields.Text(string="Full Name of Work", required=True)

    client = fields.Char(string="Client")
    project_ecv = fields.Char(string="Estimated Cost of Project", readonly=True, store=True)
    rebate = fields.Char(string="Percentage (+/-)", required=True)
    quoted_total = fields.Char(string='Quoted Cost Value of the Work', store=True, readonly=True)

    work_order_number = fields.Char(string="Client Work Order No.", copy=False)
    work_order_date = fields.Date(string='Work Order Date', required=True, index=True)
    completion_date = fields.Date(string='Estimated Completition Date', required=True, index=True)

    completion_time = fields.Integer(string="Completion time (in Days)",
                                     required=True, index=True, store=False)
    remaining_completition_days = fields.Integer(string="Remaining Completion Time (in Days)")
    currency_id = fields.Many2one(related='mb_line.currency_id', depends=['mb_line.currency_id'], store=True,
                                  string='Currency')
    mb_line = fields.One2many('mb.entry.line', 'mb_id', string='Measurement Book', copy=True, auto_join=True, readonly=True)




    @api.onchange('project')
    def project_onchange(self):
        for rec in self:
            if rec.project:
                rec.project_short = rec.project.project_short
                rec.project_desc = rec.project.project_desc


#    def default_get(self):
class mb_entry_line(models.Model):
    _name = 'mb.entry.line'
    _description = "Measurement Book Lines"
    _rec_name = 'mb_id'
    mb_id = fields.Many2one('mb.entry',string='MB Lines ID', index=True,
                               copy=False)

    item_id = fields.Char(string="SNo.", store=True, readonly=True)
    item_short = fields.Char(string='Item', store=True, readonly=True)
    item_qty = fields.Float(string="Estimated QTY.", required=True, digits=(30, 3), store=True, readonly=True)
    boq_id = fields.Char(string='BOQ ID')
    item_des = fields.Text(string='Item Description', store=True)
    item_rate = fields.Monetary(string="SOR Rate", required=True, store=True,)
    uom = fields.Char(string='Per', store=True)
    amount = fields.Monetary(readonly=True, string="Amount", required=True, strore=True)
    currency_id = fields.Many2one('res.currency', string='Currency')