Rails Activerecord adding columns to multiple tables

Question

I need to make a migration where a column is added to three separate tables. The views column is an integer and needs to also default => 0. How can I add these columns with activerecord commands? I am using postgreSQL database.

Here is how my migration should look like:

class AddViewsToRestaurantsMenusDishes < ActiveRecord::Migration[6.0]
   def change
     add_column Restaurant, :views, :integer, :default => 0
     add_column Menu, :views, :integer, :default => 0
     add_column Dish, :views, :integer, :default => 0
   end
end

I can't find where it says how to add columns for multiple tables and how to set default => 0 — Jabba the Hutt
– Jabba the Hutt, Commented Feb 6, 2020 at 6:22
Have you tried add_column :restaurants, :views, :integer, default: 0? Repeat two times, changing :restaurants to :menus and :dishes? — jvillian
– jvillian, Commented Feb 6, 2020 at 6:27
Its not correct with that command. And I saw somewhere where a migration was using model names as the first argument which also struck me as odd. — Jabba the Hutt
– Jabba the Hutt, Commented Feb 6, 2020 at 6:39
"add_column :restaurants, :views, :integer, default: 0" makes an empty migration. The correct way is "AddViewsToTeams views:integer". But that doesn't make it look like the example above where the model is the first argument. And adding default:0 after views:integer just makes it another column instead of making the views default => 0 — Jabba the Hutt
– Jabba the Hutt, Commented Feb 6, 2020 at 6:56

max · Accepted Answer · 2020-02-06 15:07:45Z

add_column(table_name, column_name, type, **options)

class AddViewsToRestaurantsMenusDishes < ActiveRecord::Migration[6.0]
   def change
     add_column :restaurants, :views, :integer, default: 0
     add_column :menus, :views, :integer, default: 0
     add_column :dishes, :views, :integer, default: 0
   end
end

None of the methods in ActiveRecord::ConnectionAdapters::SchemaStatements or ActiveRecord::ConnectionAdapters::TableDefinition which make up the whole migrations DSL take models as arguments - its all tables all the way.

This assumes that your tables are conventionally named. If you really wanted to do the same thing from a list of model classes you could do:

class AddViewsToRestaurantsMenusDishes < ActiveRecord::Migration[6.0]
   def change
     [Restaurant, Menu, Dish].each do |model|
       add_column model.table_name, :views, :integer, default: 0
     end
   end
end

But for migrations its usually a good idea to KISS. Especially since they are not supposed to stick around for the entire lifetime of your project.

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