Rails API provides a useful feature called Console. The console is an interactive tool for testing the code in our Rails application.
Before opening a console session, let us define a Person model with name and age columns.
rails generate model Person name:string age: integer
invoke active_record
create db/migrate/20250227112053_create_people.rb
create app/models/person.rb
invoke test_unit
create test/models/person_test.rb
create test/fixtures/people.yml
This will create Person class derived from ApplicationRecord:
classPerson<ApplicationRecordend
As in the previous chapter, run the migration on this model.
PSC:\Users\mlath\RubymineProjects\library> rails db:migrate==20250227112053CreatePeople: migrating =====================================-- create_table(:people)->0.0230s
==20250227112053CreatePeople: migrated (0.0247s)==============================20250227112941Persons: migrating ============================================20250227112941Persons: migrated (0.0000s)=================================
Open a PowerShell or Command prompt if using Windows, or a terminal if on Ubuntu. Make sure that you are logged into the project directory (library in this case).
PSC:\Users\mlath\RubymineProjects\library> rails console
Loading development environment (Rails8.0.1)
library(dev)>
You can check the version of Rails installation in the console window.
library(dev)>Rails.version
=>"8.0.1"
All the resources of the project, including the Person model can be accessed in the console. To get the list of columns defined in Person model, use column_names property.
library(dev)>Person.column_names
=>["id","name","age","created_at","updated_at"]
Note that Rails adds created_at and updated_at columns.
The new() function of the Person class creates a new Person object.
library(dev)> p1 =Person.new(name:"Ravi", age:21)=>#<Person:0x000002ac6815e228 id: nil, name: "Ravi",
age:21, created_at:nil, updated_at:nil>
The object is placed in the memory. To save it persistently in the database, call the save() function.
library(dev)> p1.save
TRANSACTION(0.6ms)BEGIN/*application='Library'*/TRANSACTION(0.7ms)BEGIN/*application='Library'*/PersonCreate(4.6ms)INSERTINTO"people"("name","age","created_at","updated_at")VALUES('Ravi',21,'2025-02-27 12:29:12.006534','2025-02-27 12:29:12.006534')RETURNING"id"/*application='Library'*/TRANSACTION(1.5ms)COMMIT/*application='Library'*/=>true
The auto-created fields created_at and updated_at bear the time stamp:
library(dev)> p1
=>#<Person:0x000002ac6815e228
id:1,
name:"Ravi",
age:21,
created_at:"2025-02-27 12:29:12.006534000 +0000",
updated_at:"2025-02-27 12:29:12.006534000 +0000">
The create() function creates a new object and save it in the database.
library(dev)>Person.create(name:"Raja", age:25)TRANSACTION(1.0ms)BEGIN/*application='Library'*/PersonCreate(2.8ms)INSERTINTO"people"("name","age","created_at","updated_at")VALUES('Raja',25,'2025-02-27 12:30:33.474115','2025-02-27 12:30:33.474115')RETURNING"id"/*application='Library'*/TRANSACTION(39.1ms)COMMIT/*application='Library'*/=>#<Person:0x000002ac690d6908
id:2,
name:"Raja",
age:25,
created_at:"2025-02-27 12:30:33.474115000 +0000",
updated_at:"2025-02-27 12:30:33.474115000 +0000">
The all() function retrieves all the records in the underlying table.
library(dev)>Person.all
PersonLoad(1.0ms)SELECT"people".*FROM"people"/* loading for pp */LIMIT11/*application='Library'*/=>[#<Person:0x000002ac690dc588
id:1,
name:"Ravi",
age:21,
created_at:"2025-02-27 12:29:12.006534000 +0000",
updated_at:"2025-02-27 12:29:12.006534000 +0000">,#<Person:0x000002ac690dc308
id:2,
name:"Raja",
age:25,
created_at:"2025-02-27 12:30:33.474115000 +0000",
updated_at:"2025-02-27 12:30:33.474115000 +0000">]
Rails also adds id as the primary ley for the model. You can fetch a given record by calling the find() function and giving id as an argument.
To find the record with id=1 −
library(dev)> p1=Person.find(1)PersonLoad(0.9ms)SELECT"people".*FROM"people"WHERE"people"."id"=1LIMIT1/*application='Library'*/=>#<Person:0x000002ac690db048...
To modify a record, assign a new value to one or more attributes (columns) and call save() function. Let us change the name of person with id=1 to Ravindra.
library(dev)> p1.name="Ravindra"=>"Ravindra"
library(dev)> p1.save
TRANSACTION(0.6ms)BEGIN/*application='Library'*/PersonUpdate(4.2ms)UPDATE"people"SET"name"='Ravindra',"updated_at"='2025-02-27 12:34:14.306655'WHERE"people"."id"=1/*application='Library'*/TRANSACTION(38.3ms)COMMIT/*application='Library'*/=>true
Note that Rails translates this function call to the equivalent UPDATE query.
You can apply filter to conditionally fetch records from the underlying table. You can use all the comparison operators in the where() function.
library(dev)>Person.where("age > ?",25)PersonLoad(1.7ms)SELECT"people".*FROM"people"WHERE(age >25)/* loading for pp */LIMIT11/*application='Library'*/=>[#<Person:0x000002ac6993ac98
id:2,
name:"Raja",
age:30,
created_at:"2025-02-27 12:30:33.474115000 +0000",
updated_at:"2025-02-27 12:36:04.560314000 +0000">]
Here also Rails internally executes an equivalent SELECT query .
The update() function works as an equivalent foe assigning new value to a column and calling save() function. Let us update the name of a record with id=2.
library(dev)> p1.update(name:"Rajendra")TRANSACTION(0.6ms)BEGIN/*application='Library'*/PersonUpdate(2.9ms)UPDATE"people"SET"name"='Rajendra',"updated_at"='2025-02-27 12:38:06.880558'WHERE"people"."id"=2/*application='Library'*/TRANSACTION(38.8ms)COMMIT/*application='Library'*/=>true
How can you delete a record from the table? Let us first add a new record , Rails assigns a unique id to it.
library(dev)>Person.create(name:"Roger", age:20)TRANSACTION(0.9ms)BEGIN/*application='Library'*/PersonCreate(2.9ms)INSERTINTO"people"("name","age","created_at","updated_at")VALUES('Roger',20,'2025-02-27 12:40:00.051918','2025-02-27 12:40:00.051918')RETURNING"id"/*application='Library'*/TRANSACTION(39.3ms)COMMIT/*application='Library'*/=>#<Person:0x000002ac69935f18
id:3,
name:"Roger",
age:20,
created_at:"2025-02-27 12:40:00.051918000 +0000",
updated_at:"2025-02-27 12:40:00.051918000 +0000">
library(dev)> p1 =Person.find(3)PersonLoad(0.9ms)SELECT"people".*FROM"people"WHERE"people"."id"=3LIMIT1/*application='Library'*/=>#<Person:0x000002ac6993e9d8...
To delete an instance of the Person model, call the destroy function.
library(dev)> p1.destroy
TRANSACTION(0.6ms)BEGIN/*application='Library'*/PersonDestroy(2.0ms)DELETEFROM"people"WHERE"people"."id"=3/*application='Library'*/TRANSACTION(39.6ms)COMMIT/*application='Library'*/=>#<Person:0x000002ac6993e9d8
id:3,
name:"Roger",
age:20,
created_at:"2025-02-27 12:40:00.051918000 +0000",
updated_at:"2025-02-27 12:40:00.051918000 +0000">
This executes the DELETE query as can be seen from the console log.
Most of the actions required to create and manage a Rails application are performed using various commands. For example Rails new creates the directory structure for a new application, Rails generate allows you to generate components such as ActiveRecord and migrations.
Here is the list of Rails commands:
- bin/rails console
- bin/rails server
- bin/rails test
- bin/rails generate
- bin/rails db:migrate
- bin/rails db:create
- bin/rails routes
- bin/rails dbconsole
- rails new app_name
The dbconsole is also another useful console command. It opens the console of the corresponding database which you have used as a backend for your application. In this case, the library application has been created with PostgreSQL as the backend. Hence, dbconsole opens the psql console.
C:\Users\mlath\RubymineProjects\library>rails dbconsole
Passwordfor user postgres:
psql (16.2)WARNING:Console code page (437) differs from Windows code page (1252)8-bit characters might not work correctly.See psql reference
page "Notes for Windows users"for details.Type"help"for help.
library_development=#
