Rails migration for change column

Question

We have script/generate migration add_fieldname_to_tablename fieldname:datatype syntax for adding new columns to a model.

On the same line, do we have a

Answer 1

You can also use a block if you have multiple columns to change within a table.

Example:

change_table :table_name do |t|
  t.change :column_name, :column_type, {options}
end

See the API documentation on the Table class for more details.

Answer 2

As I found by the previous answers, three steps are needed to change the type of a column:

Step 1:

Generate a new migration file using this code:

rails g migration sample_name_change_column_type

Step 2:

Go to /db/migrate folder and edit the migration file you made. There are two different solutions.

1. def change
       change_column(:table_name, :column_name, :new_type)
   end
   

2.

    def up
        change_column :table_name, :column_name, :new_type
    end

    def down
        change_column :table_name, :column_name, :old_type
    end

Step 3:

Don't forget to do this command:

rake db:migrate

I have tested this solution for Rails 4 and it works well.

Answer 3

To complete answers in case of editing default value :

In your rails console :

rails g migration MigrationName

In the migration :

  def change
    change_column :tables, :field_name, :field_type, default: value
  end

Will look like :

  def change
    change_column :members, :approved, :boolean, default: true
  end