Rails ActiveRecord Console Commands
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.
| id | username | password |
|---|---|---|
| 1 | Alex | al23lk@#$AFfFj23rhf0a98eraljkwqer |
| 2 | Benny | 2llLKJ#3j3#KJ#L7ouOuoI# |
| 7 | Carlton | #LKJ#LkjJ9f9wf0j |
| id | user_id | pet_name |
|---|---|---|
| 1 | 2 | Scruffy |
| 2 | 2 | Buddy |
| 3 | 3 | Buttons |
Viewing a record
To view the first user:
2.1.1 :003 > User.first
=> #<User id: 1, username: "Alex", password: "al23lk@#$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: "al23lk@#$AFfFj23rhf0a98eraljkwqer">
2.1.1 :013 > a
=> #<User id: 1, username: "Alex", password: "al23lk@#$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: "al23lk@#$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")