Rails ActiveRecord API

Question 1 of 10

1

Assuming we are following Rails conventions, and given the following domain models:


class Vehicle < ActiveRecord::Base
  has_one :engine
end
class Engine < ActiveRecord::Base
  belongs_to :vehicle
end

Which of the following database table columns will exist to support this association.

Select one or more of the following:

```
vehicles.engine_id
```
```
engines.engine_id
```
```
engines.vehicle_id
```
```
vehicles.vechicle_id
```

Explanation

Question 2 of 10

1

Given the following model, what is output from the last line:


class Person < ActiveRecord::Base
  validates :name, presence: true
end

Person.create(name: nil)

Select one of the following:

A Person instance
An ActiveRecord::RecordInvalid error is raised
false
true

Explanation

Question 3 of 10

1

Given the following domain model:


class User < ActiveRecord::Base
end
User.all.map(&:id)
=> [1, 2, 3, 4, 5]

Which of the following statements can be used to delete User instances with IDs 2 and 4:

Select one or more of the following:


User.find_by_id([2,4]).each(&:destroy)

```
User.destroy([2,4])
```
```
User.find([2,4]).each(&:destroy)
```
```
User.where(id: [2,4]).each(&:destroy)
```

Explanation

Question 4 of 10

1

Given the following domain model:


class User < ActiveRecord::Base
end
User.all.map(&:id)
=> [1, 2, 3, 4, 5]

Which of the following statements can be used to delete User instances with IDs 2 and 4:

Select one or more of the following:


User.find_by_id([2,4,99]).each(&:destroy)

```
User.destroy([2,4,99])
```
```
User.find([2,4,99]).each(&:destroy)
```


User.where(id: [2,4,99]).each(&:destroy)

Explanation

Question 5 of 10

1

Assuming we are following Rails conventions, and given the following domain models:


class Comment < ActiveRecord::Base
  belongs_to :commentable, polymorphic: true
  has_many :comments, as: :commentable
end
class Post < ActiveRecord::Base
  has_many :comments, as: :commentable
end

Which database columns will, necessarily, exist to support these relationships

Select one of the following:

```
posts.comment_id, comments.comment_id
```

comments.commentable_type, comments.commentable_id

```
comments.id, comments.type
```
```
commentables.id, commentables.type
```

Explanation

Question 6 of 10

1

Given the following domain model


class Post < ActiveRecord::Base
  validates :title, presence: true

  before_create { puts "Before create" }
  before_save { puts "Before save" }
  before_update { puts "Before update" }
  before_validation { puts "Before validation" }
end

What is correct sequence of output, from the puts statements above, as triggered by the following:


p = Post.new(title: "Dummy title")
p.save
p.save

Select one of the following:

Before validation
Before save
Before create
Before validation
Before save
Before update
Before validation
Before create
Before save
Before validation
Before update
Before save
Before validation
Before save
Before create
Before validation
Before update
Before validation
Before save
Before create
Before save
Before update
Before save
Before validation
Before create
Before save
Before validation
Before update

Explanation

Question 7 of 10

1

Select from the dropdown list to complete the text.

Complete the following code such that the statement "Just going to get on with things" is output:


class User < ActiveRecord::Base
  validates :name, presence: true
end
begin
  ActiveRecord::Base.transaction do
    @new_user = User.create(name: nil)
    raise ( ActiveRecord::Rollback, Exception, ActiveRecord::RecordInvalid, ArgumentError ) unless @new_user.persisted?
  end
  puts "Just going to get on with things"
rescue StandardError => e
  puts "Just caught an error"
end

Explanation

Question 8 of 10

1

Assuming we are following Rails conventions, and given the following domain models:


class Vehicle < ActiveRecord::Base
  self.abstract_class = true
end
class Automobile < Vehicle; end
class Car < Automobile; end

Car.create!

Which database tables will need to exist to allow us to persist a Car instance

Select one of the following:

```
vehicles
```
```
cars
```
```
cars and automobiles
```
```
cars, automobiles and vehicles
```
```
automobiles
```

Explanation

Question 9 of 10

1

Given the following domain models:


class User < ActiveRecord::Base
  has_many :posts
end
class Post < ActiveRecord::Base
  validates :title, presence: true
  belongs_to :user
end

Regardless of the data in the DB, which of the following patterns will issue a single SQL statement to the database:

Select one or more of the following:

users = User.includes(:posts); users.each{ |u| u.posts.to_a }

users = User.preload(:posts); users.each{ |u| u.posts.to_a }

users = User.joins(:posts); users.each{ |u| u.posts.to_a }

users = User.includes(:posts).where(posts: {title: "Dummy"}); users.each{ |u| u.posts.to_a }

users = User.eager_load(:posts); users.each{ |u| u.posts.to_a }

Explanation

Question 10 of 10

1

Select from the dropdown list to complete the text.

Complete the Foo class below such that the final create statement will lead to a new Foo record persisted to the database:


class Foo < ActiveRecord::Base
  validates :name, presence: true
  ( after_commit, before_validation, after_validation, before_save, after_create ) { throw :abort }
end

Foo.create(name: "bar")

Think you know the Rails ActiveRecord API? Have a go at this 10-question quiz to see how complete that knowledge is.

Rails ActiveRecord API

Rails ActiveRecord API

Question 1 of 10

Assuming we are following Rails conventions, and given the following domain models:
`class Vehicle < ActiveRecord::Base has_one :engine end class Engine < ActiveRecord::Base belongs_to :vehicle end`

Which of the following database table columns will exist to support this association.

Select one or more of the following:

Explanation

Question 2 of 10

Given the following model, what is output from the last line:
`class Person < ActiveRecord::Base validates :name, presence: true end Person.create(name: nil)`

Select one of the following:

Explanation

Question 3 of 10

Given the following domain model:
`class User < ActiveRecord::Base end User.all.map(&:id) => [1, 2, 3, 4, 5]`

Which of the following statements can be used to delete User instances with IDs 2 and 4:

Select one or more of the following:

Explanation

Question 4 of 10

Given the following domain model:
`class User < ActiveRecord::Base end User.all.map(&:id) => [1, 2, 3, 4, 5]`

Which of the following statements can be used to delete User instances with IDs 2 and 4:

Select one or more of the following:

Explanation

Question 5 of 10

Select one of the following:

Explanation

Question 6 of 10

Select one of the following:

Explanation

Question 7 of 10

Select from the dropdown list to complete the text.

Explanation

Question 8 of 10

Select one of the following:

Explanation

Question 9 of 10

Given the following domain models:
`class User < ActiveRecord::Base has_many :posts end class Post < ActiveRecord::Base validates :title, presence: true belongs_to :user end`

Regardless of the data in the DB, which of the following patterns will issue a single SQL statement to the database:

Select one or more of the following:

Explanation

Question 10 of 10

Select from the dropdown list to complete the text.

Explanation

	Created by Domhnall Murphy almost 2 years ago

Think you know the Rails ActiveRecord API? Have a go at this 10-question quiz to see how complete that knowledge is.

Rails ActiveRecord API

Rails ActiveRecord API

Question 1 of 10

Assuming we are following Rails conventions, and given the following domain models: class Vehicle < ActiveRecord::Base has_one :engine end class Engine < ActiveRecord::Base belongs_to :vehicle end Which of the following database table columns will exist to support this association.

Select one or more of the following:

Explanation

Question 2 of 10

Given the following model, what is output from the last line: class Person < ActiveRecord::Base validates :name, presence: true end Person.create(name: nil)

Select one of the following:

Explanation

Question 3 of 10

Given the following domain model: class User < ActiveRecord::Base end User.all.map(&:id) => [1, 2, 3, 4, 5] Which of the following statements can be used to delete User instances with IDs 2 and 4:

Select one or more of the following:

Explanation

Question 4 of 10

Given the following domain model: class User < ActiveRecord::Base end User.all.map(&:id) => [1, 2, 3, 4, 5] Which of the following statements can be used to delete User instances with IDs 2 and 4:

Select one or more of the following:

Explanation

Question 5 of 10

Select one of the following:

Explanation

Question 6 of 10

Select one of the following:

Explanation

Question 7 of 10

Select from the dropdown list to complete the text.

Explanation

Question 8 of 10

Select one of the following:

Explanation

Question 9 of 10

Given the following domain models: class User < ActiveRecord::Base has_many :posts end class Post < ActiveRecord::Base validates :title, presence: true belongs_to :user end Regardless of the data in the DB, which of the following patterns will issue a single SQL statement to the database:

Select one or more of the following:

Explanation

Question 10 of 10

Select from the dropdown list to complete the text.

Explanation

Assuming we are following Rails conventions, and given the following domain models:
`class Vehicle < ActiveRecord::Base has_one :engine end class Engine < ActiveRecord::Base belongs_to :vehicle end`

Which of the following database table columns will exist to support this association.

Given the following model, what is output from the last line:
`class Person < ActiveRecord::Base validates :name, presence: true end Person.create(name: nil)`

Given the following domain model:
`class User < ActiveRecord::Base end User.all.map(&:id) => [1, 2, 3, 4, 5]`

Which of the following statements can be used to delete User instances with IDs 2 and 4:

Given the following domain model:
`class User < ActiveRecord::Base end User.all.map(&:id) => [1, 2, 3, 4, 5]`

Which of the following statements can be used to delete User instances with IDs 2 and 4:

Given the following domain models:
`class User < ActiveRecord::Base has_many :posts end class Post < ActiveRecord::Base validates :title, presence: true belongs_to :user end`

Regardless of the data in the DB, which of the following patterns will issue a single SQL statement to the database: