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Living on the edge (of Rails) #19 - change_table for migrations and more

May 4, 2008

This week’s report covers changes from 29 April 2008 to 4th May 2008 (the day the corresponding Rails Envy podcast was recorded).

change_table for ActiveRecord migrations

Thanks to Jeff Dean, who also blogged about the new change_table feature in ActiveRecord migrations, you can now change a table with a block like so:

change_table :videos do |t|
  t.add_timestamps
  t.add_belongs_to :goat
  t.add_string :name, :email, :limit => 20
  t.remove_column :name, :email # takes multiple arguments
  t.rename :new_name
  t.string :new_string_column # executes against the renamed table name
end

Some key things to note:

• add_XXX would add a new column for you, e.g. add_string would add a new string field.
• Of course, add_timestamps would add the magic created_at and updated_at datetime fields.
• remove_column now takes multiple arguments.
• rename would rename the table.

Very nice, DRY enhancement, props to Jeff Dean once again.

Related changeset: http://github.com/rails/rails/commit/96980bd561d79824b6cb6efbcbecdcbf8785d452

ActiveRecord::Base.create takes a block like ActiveRecord::Base.new

Yup now you can also create ActiveRecord objects with a block argument just like you could for ActiveRecord::Base.new:

@person = Person.create(params[:person]) do |p|
  p.name = 'Konata Izumi'
  p.age = 17
end

Credit goes to Adam Meehan for this patch.

Related changeset: http://github.com/rails/rails/commit/dd120ede53eaf71dee76894998a81626b7a689fc

Bugfix: change_column should be able to use :null => true on a field that
formerly had false

You can now use change_column in your migrations to alter a column as nullable if it was previously NOT NULL.

This bugfix is courtesy of Nate Wiger.

Related changeset: http://github.com/rails/rails/commit/10ef65a3b054270ed3d458ec8eb7c2b9a3e638f7

As always, let me know of any suggestions or how I can improve the Living on the Edge (of Rails) series.

Posted by Chu Yeow at May 4, 2008 SGT | Permalink | | Category: Open Source, Ruby, Ruby on Rails