Question

I was under the impression that with Rails you’re not supposed to define any dependencies in the database, but rather just use your has_many and belongs_to stuff to define relationships. However, I’m going through the rails guide, and it has the following.

class CreateComments < ActiveRecord::Migration
  def change
    create_table :comments do |t|
      t.string :commenter
      t.text :body
      t.references :post

      t.timestamps
    end

    add_index :comments, :post_id
  end
end

I thought this wasn’t okay…? I’m trying to do something like a comment field that creates a new instance each time you call the show method, but I think without these “references” and “add_index,” it’s not storing the post_id in the comment row.

Answer 1

All this migration does is create post_id and tells the database that it should index this column (improves performance)

t.references :post is basically the same as t.integer :post_id so, yes, it is storing the post_id in the comment. You’ll still need to define your relationships in your models.