What is happening under the hood when executing this?
rails generate migration create_menu_categories_and_menu_items
Why can't I just create a file in the migrations directory? It seems I have to use the generate command in order for it to actually run, but the only file I see changed is the file created by the above command.
You can, but you need to get the time stamp at the beginning of the file name, so that rails can figure out that it's a "pending migration" and run it. It does this by storing the time stamp (or version in migration parlance) in a special database table (schema_migrations) and anything newer than the last run migration is pending.
Otherwise there's nothing special about the file itself
You dont even have to create a separate migration file. You can just add a column to your table by adding the object to to your current migration class like this:
t.string :name
Then run a rake db:migrate
Hope this helps.
