Active Record pattern in Ruby on Rails - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to find a user by id using Active Record.

Ruby on Rails

user = User.[1](1)

Drag options to blanks, or click blank then click option'

Afind

Bget

Csearch

Dlookup

Attempts:

3 left

💡 Hint

Common Mistakes

Using methods like 'get' or 'search' which do not exist in Active Record.

The find method retrieves a record by its primary key in Active Record.

2fill in blank

medium

Complete the code to create a new user record with Active Record.

Ruby on Rails

user = User.[1](name: "Alice", email: "[e-mail]")

Drag options to blanks, or click blank then click option'

Amake

Bbuild

Cnew_record

Dcreate

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'build' which only builds but does not save the record.

The create method builds and saves a new record in one step.

3fill in blank

hard

Fix the error in the code to update a user's email attribute.

Ruby on Rails

user = User.find(1)
user.[1](email: "[e-mail]")

Drag options to blanks, or click blank then click option'

Aupdate

Bchange

Cmodify

Dedit

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'change' or 'edit' which are not Active Record methods.

The update method changes attributes and saves the record.

4fill in blank

hard

Fill both blanks to query users with age greater than 30 and order by name.

Ruby on Rails

users = User.where("age [1] ?", 30).[2](:name)

Drag options to blanks, or click blank then click option'

A>

Border

C<

Dsort

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' instead of '>' for filtering.

Using 'sort' which is not an Active Record method.

The where method filters records; use '>' to find ages greater than 30. The order method sorts results by a column.

5fill in blank

hard

Fill all three blanks to define a scope named 'active' that selects users with status 'active' and orders by created_at descending.

Ruby on Rails

scope :active, -> { where(status: [1]).[2](created_at: [3]) }

Drag options to blanks, or click blank then click option'

A"active"

Border

C:desc

D"inactive"

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'inactive' instead of 'active' for status.

Using incorrect method names for ordering.

The scope filters users with status 'active', orders them by created_at in descending order using order and :desc.

Practice

1. What is the main purpose of the Active Record pattern in Rails?

easy

A. To link Ruby classes with database tables for easy data management

B. To create user interfaces with Ruby code

C. To handle HTTP requests and responses

D. To style web pages using CSS

Solution

1. Step 1: Understand Active Record's role

   Active Record connects Ruby classes to database tables, making data handling easier.

2. Step 2: Compare options to this role

   Only To link Ruby classes with database tables for easy data management describes this connection; others describe unrelated tasks.

3. Final Answer:

   To link Ruby classes with database tables for easy data management -> Option A

4. Quick Check:

   Active Record = Ruby class to DB table link [OK]

Hint: Active Record links Ruby classes to tables [OK]

Common Mistakes:

• Confusing Active Record with view or controller roles
• Thinking it handles HTTP or styling
• Assuming it writes SQL directly

2. Which of the following is the correct way to find a record by its ID using Active Record?

easy

A. User.find_by_id(5)

B. User.where(id: 5).first!

C. User.find(5)

D. User.get(5)

Solution

1. Step 1: Recall Active Record find methods

   The method find fetches a record by its ID directly.

2. Step 2: Check each option

   User.find(5) uses find(5), which is correct. User.find_by_id(5) is deprecated. User.where(id: 5).first! is valid but less direct. User.get(5) is invalid.

3. Final Answer:

   User.find(5) -> Option C

4. Quick Check:

   Use find(id) to get record by ID [OK]

Hint: Use find(id) to get record by ID [OK]

Common Mistakes:

• Using deprecated find_by_id instead of find
• Using invalid method names like get
• Confusing where.first! with find for simple ID lookup

3. Given the code:

user = User.find(3)
user.update(name: "Alice")
puts user.name

What will be printed?

medium

A. Alice

B. An error message

C. nil

D. 3

Solution

1. Step 1: Understand the update method

   The update method changes the record's attributes and saves it.

2. Step 2: Check the output of puts user.name

   After updating, user.name is "Alice", so it prints "Alice".

3. Final Answer:

   Alice -> Option A

4. Quick Check:

   update changes attribute, then prints new value [OK]

Hint: update changes and saves record attributes [OK]

Common Mistakes:

• Thinking update returns the ID
• Assuming update does not save changes
• Expecting nil or error without reason

4. What is wrong with this code snippet?

post = Post.find(10)
post.title = "New Title"
post.save!

medium

A. Using save! will not save changes

B. No error; this code correctly updates the post title

C. Assigning title directly is not allowed

D. find(10) returns an array, not a single record

Solution

1. Step 1: Analyze the code actions

   The code finds a post by ID, changes its title, then saves it with save!.

2. Step 2: Check if any step is invalid

   Assigning attributes directly and using save! is valid and will update the record.

3. Final Answer:

   No error; this code correctly updates the post title -> Option B

4. Quick Check:

   Direct attribute assignment + save! updates record [OK]

Hint: Direct attribute change + save! updates record [OK]

Common Mistakes:

• Thinking save! does not save changes
• Believing find returns an array
• Assuming direct assignment is forbidden

5. You want to get all users who signed up after January 1, 2023, and order them by their signup date descending. Which Active Record query is correct?

hard

A. User.select_all.where(created_at > '2023-01-01').order_desc('created_at')

B. User.find_by(created_at: '> 2023-01-01').sort(created_at: :desc)

C. User.filter(created_at > '2023-01-01').order_by('created_at desc')

D. User.where('created_at > ?', '2023-01-01').order(created_at: :desc)

Solution

1. Step 1: Identify correct where syntax

   Active Record uses where('created_at > ?', date) to filter by date.

2. Step 2: Identify correct order syntax

   Ordering is done with order(created_at: :desc) for descending order.

3. Step 3: Compare options

   Only User.where('created_at > ?', '2023-01-01').order(created_at: :desc) uses correct where and order syntax; others use invalid or non-existent methods.

4. Final Answer:

   User.where('created_at > ?', '2023-01-01').order(created_at: :desc) -> Option D

5. Quick Check:

   where + order with symbols = correct query [OK]

Hint: Use where with ? and order with symbol for sorting [OK]

Common Mistakes:

• Using find_by instead of where for multiple records
• Using non-existent methods like filter or order_desc
• Incorrect syntax in where clause