Screamers 
Generate a migration file that converts column types all at once.
Installation
Add this line to your Rails application's Gemfile:
gem 'screamers'
And then execute:
% bundle
The following subcommand will be added to the rails g command.
Screamers:
screamers:migration
Synopsis
bin/rails g screamers:migration <old-column-type> <new-column-type>
Usage
Here is an example of converting date type to datetime type.
% bin/rails g screamers:migration date datetime
create db/migrate/20170628144908_change_date_to_datetime_using_screamers.rb
Generate a migration file that converts column types all at once.
Development
After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.
To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.
Contributing
Bug reports and pull requests are welcome on GitHub at https://github.com/koic/screamers.
License
The gem is available as open source under the terms of the MIT License.