31_Intro_to_tables_migrations_rails_conventions.txt

Intro to tables, migrations, rails conventions - text references
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You can take a look at all code-changes made in this video at: https://github.com/udemyrailscourse/alpha-blog-6/commit/05b1ad6dd72231f3d2ea378479d88d4bf68848ad

The additions are shown in green and removals are shown in red.

Details
Model name: article

Class name: Article -> Capitalized A and singular, CamelCase

File name: article.rb -> singular and all lowercase, snake_case

Table name: articles -> plural of model name and all lowercase

Additional example:

Model name: user

Class name: User -> Capitalized U and singular, CamelCase

File name: user.rb -> singular and all lowercase, snake_case

Table name: users -> plural of model name

Generate a migration to create a table (in this example articles):

rails generate migration create_articles

To add attributes for the table in the migration file, add the following inside create_table block:

t.string :title

To run the migration file, run the following command from the terminal:

rails db:migrate

The first time you run the migration file, it will create the database, the articles table and a schema.rb file.

To rollback or undo the changes made by the last migration file that was run, you may use the following command:

rails db:rollback

If you have run the rollback step, then you can update the previous migration file and add the following line to add a description attribute (column) to the articles table:

t.text :description
To run the newly edited migration file again, you can run rails db:migrate

Note: This above line will only work if you had rolled back the prior migration.

To generate a new migration file to add or make changes to your articles table you can generate a new file:

rails generate migration name_of_migration_file

Then within the def change method in the migration file you can add the following lines:

add_column :articles, :created_at, :datetime
add_column :articles, :updated_at, :datetime
You can run the newly created migrations file by running rails db:migrate from the command line and check out the schema.rb file to check that the changes were reflected properly.