class PurchaseRequest:
    __metaclass__ = PoolMeta
    __name__ = 'purchase.request'
    employee = fields.Function(fields.Many2One('company.employee', 'Employee',
        states={
            'invisible': ~Eval('employee', False),
            }), 'get_employee', searcher='search_employee')
    requisition_number = fields.Function(fields.Char('Requisition Number',
        states={
            'invisible': ~Eval('requisition_number', False),
        }), 'get_requisition_number', searcher='search_requisition_number')

    def get_employee(self, name):
        pool = Pool()
        RequisitionLine = pool.get('purchase.requisition.line')
        if isinstance(self.origin, RequisitionLine):
            return self.origin.requisition.employee.id

    @classmethod
    def search_employee(cls, name, clause):
        return [('origin.requisition.employee' + clause[0].lstrip(name),)
            + tuple(clause[1:3]) + ('purchase.requisition.line',)
            + tuple(clause[3:]), ]

    def get_requisition_number(self, name):
        pool = Pool()
        RequisitionLine = pool.get('purchase.requisition.line')
        if isinstance(self.origin, RequisitionLine):
            return self.origin.requisition.number

    @classmethod
    def search_requisition_number(cls, name, clause):
        return [('origin.requisition.number' + clause[0].lstrip(name),)
            + tuple(clause[1:3]) + ('purchase.requisition.line',)
            + tuple(clause[3:]), ]

    def _order_requisition_field(name):
        def order_field(tables):
            pool = Pool()
            Requisition = pool.get('purchase.requisition')
            RequisitionLine = pool.get('purchase.requisition.line')
            field = Requisition._fields[name]
            request, _ = tables[None]
            requisitionline_table = tables.get('requisition_line')
            if requisitionline_table is None:
                requisitionline = RequisitionLine.__table__()
                requisition = Requisition.__table__()
                rline_tables = {
                    None: (requisitionline,
                        (Concat(RequisitionLine.__name__ + ',',
                                requisitionline.id)) == request.origin),
                    'requisition': (requisition, requisition.id ==
                                    requisitionline.requisition)
                    }
                tables['requisition_line'] = rline_tables
            return field.convert_order(name, rline_tables, Requisition)
        return staticmethod(order_field)
    order_employee = _order_requisition_field('employee')
    order_requisition_number = _order_requisition_field('number')