Bi-directional self-referential HABTM

rubyonrails-talk
1

Hi,

I'm having a little trouble figuring out how to make a self- referential HABTM bi-directional.

I have a Employee class. Each employee can have a couple of bosses, who are also employees. The employee class has the following HABTM:

has_and_belongs_to_many :bosses, :class_name => "Employee", :join_table => "bosses_courses", :association_foreign_key => "boss_id", :foreign_key => "employee_id"

Now this works fine.. but only one way. I can get all bosses of an employee but I can't get all employees of a boss.

In hindsight I think it probaby would have been better to use database schema now.

The solution might be to code something like a subordinate method for the employee class myself, but I'm not sure how to do that.

Does anyone has any good suggestions?

2

jeroen wrote:

Hi,

I'm having a little trouble figuring out how to make a self- referential HABTM bi-directional.

I have a Employee class. Each employee can have a couple of bosses, who are also employees. The employee class has the following HABTM:

has_and_belongs_to_many :bosses, :class_name => "Employee", :join_table => "bosses_courses", :association_foreign_key => "boss_id", :foreign_key => "employee_id"

Now this works fine.. but only one way. I can get all bosses of an employee but I can't get all employees of a boss.

In hindsight I think it probaby would have been better to use a :through relationship for this, but I can't really change the database schema now.

The solution might be to code something like a subordinate method for the employee class myself, but I'm not sure how to do that.

Does anyone has any good suggestions?

You should just be able to add

has_and_belongs_to_many :employees, :class_name => "Employee", :join_table => "bosses_courses", :association_foreign_key => "employee_id", :foreign_key => "boss_id"

Notice how I just changed the name of the relationship, and swapped the two keys. This should give you the "other" direction that you're looking for. The :class_name and :association_foreign_key arguments are probably not necessary in this one, but in this case I would keep them just to help clearly document the difference between the two relationships for myself months down the road.