Rails ActiveRecord Console Commands

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It is possible to interact with the database of a Ruby on Rails project from the console. To enter the console execute this command from the command line within your project:

rails console

In our examples below we will be using the following databases. The relationship is that a user has many pets.

users
id username password
1 Alex [email protected]#$AFfFj23rhf0a98eraljkwqer
2 Benny 2llLKJ#3j3#KJ#L7ouOuoI#
7 Carlton #LKJ#LkjJ9f9wf0j
pets
id user_id pet_name
1 2 Scruffy
2 2 Buddy
3 3 Buttons

Viewing a record

To view the first user:

2.1.1 :003 > User.first
 => #<User id: 1, username: "Alex", password: "[email protected]#$AFfFj23rhf0a98eraljkwqer"> 

To view the 3rd user:

2.1.1 :003 > User.find(3)
 => #<User id: 3, username: "Benny", password: "2llLKJ#3j3#KJ#L7ouOuoI#"> 

To find the pet with the name “Buttons”:

2.1.1 :009 > Pet.find_by_pet_name('Buttons')
 => #<Pet id: 3, user_id: 3, pet_name: "Buttons"> 

Using the where command:

2.1.1 :028 > User.where(username: "Carlton")
 => #<ActiveRecord::Relation [#<User id: 3, username: "Carlton", password: "#LKJ#LkjJ9f9wf0j">]> 

Using variables

In order to manipulate the data in the database it’s best to use variables. They are easy to use and very helpful.

To assign the first user to variable a and then display the contents of a:

2.1.1 :012 > a = User.first
 => #<User id: 1, username: "Alex", password: "[email protected]#$AFfFj23rhf0a98eraljkwqer"> 
2.1.1 :013 > a
 => #<User id: 1, username: "Alex", password: "[email protected]#$AFfFj23rhf0a98eraljkwqer"> 

To change the username for a:

2.1.1 :016 > a.username = "Alexander"
 => "Alexander" 
2.1.1 :017 > a
 => #<User id: 1, username: "Alexander", password: "[email protected]#$AFfFj23rhf0a98eraljkwqer"> 

To save the new changes to the database:

2.1.1 :018 > a.save
 => true 

If the result says ‘true’ it means the data was saved to the database. If it comes back ‘false’ it means there’s a problem and the data wasn’t saved. The validations rules still apply that are in the model. Also if you have before save filters in the model that may cause the save to fail.

Create a new record

There are two ways to create a new record. Using the ‘save’ option or ‘create’ option.

Using the save method:

2.1.1 :019 > a = User.new
 => #<User id: nil, username: nil, password: nil, created_at: nil, updated_at: nil> 
2.1.1 :020 > a.username = "Darcy"
 => "Darcy" 
2.1.1 :021 > a.save
 => true 

Using the create method:

2.1.1 :011 > User.create(:username => "Darcy")

Further reading

http://guides.rubyonrails.org/active_record_querying.html

activerecord, coding, rails

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