So I have this question:
Suppose I have these 3 models:
class Company < ActiveRecord::Base
has_many :departments
has_many :employees
end
class Department < ActiveRecord::Base
has_many :employees
belongs_to :company
end
class Employee < ActiveRecord::Base
belongs_to :company
belongs_to :department
end
Furthermore, suppose the domain I am modeling requires that I support
the existence of employees that do not belong to any department
(otherwise I would declare that Company has_many :employees, :through
=> :departments instead).
As I am working with the Department model, I am thinking that it is
conceivable that a mistake can be made in the code to allow an
employee from a company to be incorrectly assigned to a department in
another company. Hence, it might be a good idea to write some custom
validation to ensure an employee and a department belong to the same
company before they associated together.
Since associate a department and an employee together in one of two
ways, I would need validation logic in both models. So I am thinking
it would involve something like:
- In the Department model
def validate
self.errors.add(:employees, “must all belong to same company”) if
self.employees.collect { |e| e.company_id }.uniq.length > 1
end
2 In the Employee model:
def validate
self.errors.add(:department, “must belong to the same company”) if
self.department && self.department != self.company
end
However, having to write two separate methods to support a single
business rule feels not so DRY or elegant. Is there a better way to
go?
Thanks!