Rails: Adding migration to add an array (default empty)

Question

I\'m trying to add a column called share to one of my resources. The idea is that users can upload documents and share them with other (specific) users, and the array contai

Answer 1

Arrays are not normally a type to be stored in a database. As michelemina points out, you can serialize them into a string and store them, if the type of the data in the array is simple (strings, int, etc). For your case of emails, you could do this.

If, on the other hand, you want to be able to find all of the User objects that a document was shared with, there are better ways of doing this. You will want a "join table". In your case, the join-table object may be called a Share, and have the following attributes:

class Share
  belongs_to :user
  belongs_to :document
end

Then, in your Document class,

has_many :shares
has_many :users, :through => :shares

As far as generating the migration, this may be hacky, but you could create a new migration that changes the type to "string" (Edit: correct code):

class AddShareToDocuments < ActiveRecord::Migration
  def up
    change_column :documents, :share, :string
  end
  def down
    change_column :documents, :share, :array, :default => []
  end
end