ansaurus

Question

Creating Join Tables for has_many & belongs_to Associations

Answer 1

+1 A:

You have to add these columns to the schema by migrations.

http://guides.rubyonrails.org/migrations.html

Try:

script/rails generate migration AddInstanceToUsers

then go to your db/migrations folder look for the new file and make it look like:

class AddInstanceToUsers < ActiveRecord::Migration 

  def self.up 

    add_column :users, :instance_id, :integer  

  end 

  def self.down 

    remove_column :users, :instance_id

  end

end

then run

rake db:migrate

in your console.

sled 2010-09-07 16:59:35

Thanks Sled, I don't need to do anything with references? For some reason I thought Rails 3 was smart enough to do this automatically when it sees the belongs_to and has_many

AnApprentice 2010-09-07 17:01:59

Also, the user's instance_id column should have an index. Do you need to add another migration to make that happen?

AnApprentice 2010-09-07 17:12:56

Rails will _never_ change something in your schema if you change the model. You can use "t.references :instance" in your migration, see the link I posted. You can add the index in the same migration if you want. Just add the line "add_index :users, :instance_id" (without quotes of course) after the add_column.

sled 2010-09-07 17:13:16

shoot I already the migration. Does that mean it's to late to add the index?

AnApprentice 2010-09-07 17:16:34

yep.. just create another one or do a rollback, change it, and remigrate. I'd recommend to create a new migration.

sled 2010-09-07 17:30:18

So something like: script/rails generate migration AddInstanceIndexToUsers, then making sure the index is in the migration file, then running db:migrate? Is that it?

AnApprentice 2010-09-07 17:31:14

yes that's it. The name of the migration doesn't follow a convention by the way. You can name it anyway you want.

sled 2010-09-07 17:33:07

That worked, thanks for your help. I learned a ton!

AnApprentice 2010-09-07 17:40:52

ansaurus

tags:

views:

answers:

Creating Join Tables for has_many & belongs_to Associations

related questions