How to delete join table?

rubyonrails-talk
1

If you had a model instead of a has_and_belongs_to_many, you could do that.

app/models/people.rb has_many :people_roles has_many :roles, :through => :people_roles

app/models/role.rb has_many :people_roles has_many :roles, :through => :people_roles

app/models/people_role.rb belongs_to :person belongs_to :role

And then you can call PeopleRole.delete_all.

2

Thanks! I figured out another way, involving some trickery. Your way is probably more recommended.

I created a model named people_role.rb. Note the first part of the name is the plural form of Person, and the second part is the singular of the Role table. I did that because rails will pluralize the word people_role into people_roles, and people_roles is the name of my table.

Then I can call PeopleRole.delete_all and it appears to work.

3

Hmm, ran into a glitch further down the road so I redid everything your way and that works better.

For some reason each join table row had it's own id. In this case the join table columns were role_id, person_id, and id. My problem was that when saving each join table row, it was setting the id to the role_id, and since my role_id's weren't unique within the join table, the saves were failing. I have no idea why it was doing that.

4

Probably due to you creating the table like this:

create_table :people_roles do |t| t.references :person, :role

OR

t.integer :person_id, :role_id end

instead of create_table :people_roles, :id => false which would not put in that id column automatically.

5

interesting . . . next question then, why when I save a person with a role would active record be setting the id of the join row to the role_id? Since I reuse roles I was getting constraint violation type errors because it was trying to save a people_roles row the the same id as another row.

6

What was the exact error you were getting and what code were you using to get it? You should be able to assign many roles to many people and vice-versa ad infinitum ergo (and any other trippy words)

7

Hmm, I don't really have the code available, I've changed it.

Thanks for your help. It was very good.