Rails Generator CLI — 101

julio hernandez
3 min readAug 5, 2021

Losing too much time on your Coding Challenge creating your model, migrations, views and more??

It’s time to learn about a tool that helps you save some time and effort with your code. After all, aren’t we programmers lazy?? Heck Yes!!! so, let’s use the tools we have and code fast!!.

1. Model Generators

To create a model, follow this formula:

rails g model NameOfModel column_name:datatype column_name2:datatype2 --no-test-framework

For example:

rails g model Dog name:string breed:string bio:text --no-test-framework

(yes, another pet’s example! sorry not sorry)

will generate this file:

# db/migrate/20180701032833_create_dogs.rbclass CreateDogs < ActiveRecord::Migration[5.1]
def change
create_table :dogs do |t|
t.string :name
t.string :breed
t.text :bio t.timestamps

2. Migration Generators

Adding Columns

To add an additional column to a table, follow this formula:

rails g migration add_name_of_column_to_table_name name_of_column:datatype --no-test-framework

For example, if we want to add the year a dog was born, we would type in the following:

rails g migration add_year_born_to_dogs year_born:integer --no-test-framework

which will produce the following file:

# db/migrate/YYYYMMDDHHMMSS_add_year_born_to_dogs.rbclass AddYearBornToDogs< ActiveRecord::Migration[5.1]
def change
add_column :authors, :year_born, :integer

Adding multiple columns

We can also add multiple columns to the dogs table in a single CLI command like so:

rails g migration add_barks_to_dogs barks_done:integer last_game_played:string --no-test-framework

resulting in:

# db/migrate/YYYYMMDDHHMMSS_add_barks_to_dogs.rbclass AddBarksToDogs< ActiveRecord::Migration[5.1]
def change
add_column :dogs, :barks_done, :integer
add_column :dogs, :last_game_played, :string

Removing Columns

To remove a column, i.e. the last_game_played column from dogs, we can type in CLI:

rails g migration remove_last_game_played_from_dogs last_game_played:string --no-test-framework

Which creates:

#db/migrate/YYYYMMDDHHMMSS_remove_last_game_played_from_dogs.rbclass RemoveLastGamePlayedFromDogs < ActiveRecord::Migration[5.1]
def change
remove_column :dogs, :last_game_played, :string

3. Resource Generators

To create a new Model, corresponding database table, controller, and an empty views folder type in:

rails g resource ModelName column_name:datatype column_name2:datatype2 --no-test-framework

For example, if I want to create a Dog_walker model with a corresponding name that a dog will belong to:

rails g resource DogWalker first_name:string dog_id:integer --no-test-framework

4. Datatypes

Thanks to this great stack overflow post, below are the list of almost all the datatypes that Rails supports.

:string is for small data types such as a title. It’s the default type pf date.

:text is for longer pieces of textual data, i.e. paragraphs

:integer for whole numbers

:decimal for decimals

:datetime store the date and time into a column (handles timezone)

:timestamp for storing date and time into a column (timezone independent)

:binary is for storing data such as images, audio, or movies

:primary_key unique key that can uniquely identify each row in a table

:float also for decimals.

:boolean is for storing true or false values

:date store only the date

5. Don’t forget to rake:db migrate

After using your generator don’t forget to type on your terminal rake:db migrate.

generate what??

6. Resources

Still have more questions?. Here are some more in-depth resources if any additional information we might need for successfully using our generators.

Some of the information used for this blog was grabbed from the previous websites and different medium publications.