In the end, there’s some feedback about the total movies created. The seeds file uses Rails ActiveSupport, to use those handy Ruby X.ago statements to define dates. P "Created # movies" Code language: Ruby ( ruby )įirst, you destroy all movies to have a clean state and add three movies passing an array to the create method. Storyline: "Terminator 2 follows Sarah Connor and her ten-year-old son John as they are pursued by a new, more advanced Terminator: the liquid metal, shapeshifting T-1000, sent back in time to kill John Connor and prevent him from becoming the leader of the human resistance.", A young Hobbit known as Frodo has been thrown on an amazing adventure, when he is appointed the job of destroying the One Ring, which was created by the Dark Lord Sauron.", Storyline: "The Fellowship of the Ring embark on a journey to destroy the One Ring and end Sauron's reign over Middle-earth. Title: "The Lord of the Rings: The Fellowship of the Ring", Email us at or call us at 61 to learn more.Storyline: "After landing the gig of a lifetime, a New York jazz pianist suddenly finds himself trapped in a strange land between Earth and the afterlife.", If necessary, you can get the new version of rails by running the following: gem install rails -no-document Successfully installed rails-6.1.1 1 gem installed. However, for those times when your migration has some more complex logic, it’s always handy to have up and down in your back pocket!įor more than 16 years, gap intelligence has served manufacturers and sellers by providing world-class services monitoring, reporting, and analyzing the 4Ps: prices, promotions, placements, and products. To create a new app, first make sure that you’re using Rails 6.x by running rails -v. In most cases (hopefully), your database schema updates will be straightforward enough that change will be the appropriate method to use in your migrations. So we use up and down to specify what needs to be executed in the forward change and reverse for this migration. However, in this migration we call our soft delete service that executes some SQL that change doesn’t know how to handle if the migration should be reversed. If this migration was simply going to add a new column to our Advertisements Table, change would be enough here. Remove_column :advertisements, :product_version_id, :integer SoftDelete :: AddAllViews. Remove_index :advertisements, :product_version_id add_advertisements_viewĮnd def down SoftDelete :: DropAllViews. drop_advertisements_viewĪdd_column :advertisements, :product_version_id, :integerĪdd_index :advertisements, :product_version_id SoftDelete :: AddAllViews. Using the example from above again:Ĭlass AddProductVersionIdToAdvertisements < ActiveRecord :: Migration def up SoftDelete :: DropAllViews. In most cases, change accomplishes alone what up and down do together. It’s newer to Rails and the primary way to write migrations. Simply, up runs the migration, down rolls the migration back.īut what about change? As I mentioned above, the change method is more commonly used. When you run rails db:migrate, the up method is executed, whereas rails db:rollback executes the down method. In other words, the changes in up are the forward change you want to make to your db, where the changes defined in down should be changes to revert back in time. It is wise to perform the transformations in precisely the reverse order they were made in the up method. For example, if you create a table in the up method, you should drop it in the down method. As the command line implies, this tells Rails to generate a migration for us. In other words, the database schema should be unchanged if you do an up followed by a down. rails generate migration AddUserToTodos user:string invoke activerecord create db/migrate/20190428200056addusertotodos.rb. The up method should describe the transformation you’d like to make to your schema, and the down method of your migration should revert the transformations done by the up method. You can also use the old style of migration using up and down methods instead of the change method. So what exactly do they do? The Rails guide best explains it: If you’re new to Rails, or have perhaps only worked with more modern versions, up and down might not be familiar. Remove_column :downloads, :category_ids end endĭef up and def down? What’s up with that? What Goes Up Must Come Down Rename_column :downloads, :temporary_category_names, :category_names Rename_column :downloads, :category_names, :temporary_category_names end def down Class RenameCategoryNamesToCategoryIdsInDownloads < ActiveRecord :: Migration def upĪdd_column :downloads, :category_ids, :text
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