Db migrate - Add/change a default in a rails app in the `change` method

Question

I am adding a new migration to my rails app's database, in it I am adding columns to a new application. Some of the columns have defaults. I would like to add defaults to some of the existing columns as well. My code currently looks like this:

class AddStuffToTable < ActiveRecord::Migration
  def change
    add_column :table, :column4, :string
    add_column :table, :column5, :boolean, default: false
    add_default_to_column :table, :column1, default: 0
    add_default_to_column :table, :column2, default: 5.8
  end
end

I know add_default_to_column is not the correct syntax. What is the correct syntax/method name? Also, for a integer/decimal column, is the above the correct way to add a default number (I mean do I need anything other than the number itself, such as "" for a string etc.)

Answer 1

As per the rails api on ActiveRecord::Migration , you can use the following method:

change_column(table_name, column_name, type, options)

So in your case that would be:

change_column(:table, :column1, :integer, default: 0)
change_column(:table, :column2, :float, default: 5.8)

That should change your first column to an integer with a default value of 0, and your second column to a float with a default value of 5.8.

Answer 2

you may try:

add_column :table, :column5, TrueClass, :default => false

and

change_column :table, :column4,  Integer, :null => false, :default => 0

Answer 3

You don't need to specify a number as string. Check the code below for correct syntax.

class AddStuffToTable < ActiveRecord::Migration
  def change
   add_column :table, :column4, :string
   add_column :table, :column5, :boolean, :default => false
   add_column :table, :column1, :default => 0
   add_column :table, :column2, :default: => 5.8
 end
end

Answer 4

Thank you guys. I tried change_column as you suggested, and apparently there is also a change_column_default method, therefore the code is:

class AddStuffToTable < ActiveRecord::Migration
  def change
    add_column :table, :column4, :string
    add_column :table, :column5, :boolean, default: false
    change_column_default :table, :column1, default: 0
    change_column_default :table, :column2, default: 5.8
  end
end