Strong parameters in Ruby on Rails - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to permit the :name attribute in strong parameters.

Ruby on Rails

params.require(:user).permit([1])

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

A:name

B:email

C:password

D:age

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to use a symbol (missing colon).

Permitting the wrong attribute.

The permit method specifies which attributes are allowed. Here, :name is permitted.

2fill in blank

medium

Complete the code to require the :article parameter in strong parameters.

Ruby on Rails

params.[1](:article).permit(:title, :content)

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

Afetch

Ballow

Cpermit

Drequire

Attempts:

3 left

💡 Hint

Common Mistakes

Using permit instead of require.

Using a non-existent method like allow.

The require method ensures the parameter :article is present before permitting attributes.

3fill in blank

hard

Fix the error in the strong parameters method to permit :title and :body.

Ruby on Rails

def article_params
  params.require(:article).[1](:title, :body)
end

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

Arequire

Bpermit

Callow

Dfetch

Attempts:

3 left

💡 Hint

Common Mistakes

Using require twice.

Using a non-existent method like allow.

The permit method is used to allow specific attributes after requiring the parameter.

4fill in blank

hard

Fill both blanks to permit :email and :password inside the user_params method.

Ruby on Rails

def user_params
  params.[1](:user).[2](:email, :password)
end

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

Arequire

Bpermit

Cfetch

Dallow

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping the order of require and permit.

Using incorrect method names.

First, require ensures the :user parameter exists, then permit allows :email and :password.

5fill in blank

hard

Fill all three blanks to permit nested attributes :name, :email, and :profile_attributes with :age inside strong parameters.

Ruby on Rails

def user_params
  params.[1](:user).[2](:name, :email, [3]: [:age])
end

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

Arequire

Bpermit

Cprofile_attributes

Dfetch

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to permit nested attributes properly.

Using fetch instead of require.

Use require to demand :user, permit to allow attributes, and specify nested profile_attributes with :age.

Practice

1. What is the main purpose of using strong parameters in a Rails controller?

easy

A. To speed up database queries

B. To style the HTML output

C. To filter and allow only permitted attributes from user input

D. To handle user authentication

Solution

1. Step 1: Understand the role of strong parameters

   Strong parameters are used to control which attributes can be set through forms or API requests.

2. Step 2: Identify the security purpose

   This filtering prevents unwanted or harmful data from being saved, protecting against mass assignment vulnerabilities.

3. Final Answer:

   To filter and allow only permitted attributes from user input -> Option C

4. Quick Check:

   Strong parameters = filter input [OK]

Hint: Strong parameters filter input data to keep app safe [OK]

Common Mistakes:

• Thinking strong parameters speed up queries
• Confusing with styling or authentication
• Ignoring security risks of mass assignment

2. Which of the following is the correct syntax to permit the name and email attributes inside a user_params method?

easy

A. params.require(:user).permit(name, email)

B. params.permit(:user).require(:name, :email)

C. params.permit(:name, :email).require(:user)

D. params.require(:user).permit(:name, :email)

Solution

1. Step 1: Recall the correct order of methods

   The correct pattern is to first require the parent key, then permit the allowed attributes.

2. Step 2: Check the syntax for symbols

   Attributes must be symbols (with colon), so :name and :email are correct.

3. Final Answer:

   params.require(:user).permit(:name, :email) -> Option D

4. Quick Check:

   require then permit with symbols = C [OK]

Hint: Use require first, then permit with symbols [OK]

Common Mistakes:

• Swapping require and permit order
• Using attribute names without colons
• Calling permit before require

3. Given this controller code snippet:

def create
  user = User.new(user_params)
  if user.save
    render json: user
  else
    render json: user.errors
  end
end

def user_params
  params.require(:user).permit(:name, :age)
end

What happens if the incoming params include { user: { name: "Alice", age: 30, admin: true } }?

medium

A. The entire user hash is rejected

B. The admin attribute is ignored and not set on the user

C. An error is raised because admin is not permitted

D. The admin attribute is saved as true

Solution

1. Step 1: Understand permit filtering

   Only :name and :age are permitted, so admin is filtered out.

2. Step 2: Check behavior on extra params

   Extra keys are ignored silently, no error is raised, and only permitted attributes are assigned.

3. Final Answer:

   The admin attribute is ignored and not set on the user -> Option B

4. Quick Check:

   Unpermitted keys are ignored = D [OK]

Hint: Unpermitted keys are ignored, not saved or error [OK]

Common Mistakes:

• Expecting unpermitted keys to be saved
• Thinking unpermitted keys cause errors
• Assuming entire params rejected

4. Identify the error in this user_params method:

def user_params
  params.permit(:name, :email).require(:user)
end

medium

A. require should be called before permit

B. The method should use fetch instead of require

C. The attributes should be strings, not symbols

D. There is no error; the code is correct

Solution

1. Step 1: Recall correct method order

   In strong parameters, require must be called first to get the nested hash.

2. Step 2: Understand method chaining

   Calling permit before require causes an error because permit is called on the whole params, not the nested hash.

3. Final Answer:

   require should be called before permit -> Option A

4. Quick Check:

   require before permit = A [OK]

Hint: Always call require before permit in strong params [OK]

Common Mistakes:

• Swapping require and permit order
• Using strings instead of symbols (not an error)
• Thinking fetch replaces require

5. You want to allow nested attributes for a user's profile with bio and avatar_url. Which user_params method correctly permits this nested data?

hard

A. params.require(:user).permit(:name, profile: [:bio, :avatar_url])

B. params.require(:user).permit(:name, :profile => :bio, :avatar_url)

C. params.require(:user).permit(:name, :profile: [:bio, :avatar_url])

D. params.require(:user).permit(:name, :profile, :bio, :avatar_url)

Solution

1. Step 1: Understand nested attributes syntax

   To permit nested hashes, use a hash with the key and an array of permitted keys inside permit.

2. Step 2: Check each option's syntax

   params.require(:user).permit(:name, profile: [:bio, :avatar_url]) correctly uses profile: [:bio, :avatar_url]. params.require(:user).permit(:name, :profile => :bio, :avatar_url) and C have syntax errors or wrong hash style. params.require(:user).permit(:name, :profile, :bio, :avatar_url) permits keys at top level incorrectly.

3. Final Answer:

   params.require(:user).permit(:name, profile: [:bio, :avatar_url]) -> Option A

4. Quick Check:

   Nested permit uses hash with array = A [OK]

Hint: Use hash with array for nested attributes in permit [OK]

Common Mistakes:

• Passing nested keys as separate symbols
• Using wrong hash rocket syntax inside permit
• Permitting nested keys at top level