Link and URL helpers in Ruby on Rails - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the output of this Rails link_to helper?

Consider the following code in a Rails view:

link_to 'Profile', user_path(42), class: 'btn'

What HTML does this generate?

Ruby on Rails

link_to 'Profile', user_path(42), class: 'btn'

A <button class="btn">Profile</button>

B <a href="/users/42" class="btn">Profile</a>

C <a href="/profile/42" class="btn">Profile</a>

D <a class="btn">Profile</a>

💡 Hint

Remember that user_path(42) generates the URL for user with id 42.

The link_to helper creates an anchor tag with href set to the URL generated by user_path(42). The class attribute is added as specified.

📝 Syntax

intermediate

Which option correctly uses link_to with a block?

Which of the following is the correct syntax to use link_to with a block in Rails?

A

link_to(user_path(5)) do
  'Click here'
end

B link_to(user_path(5)) { 'Click here' }

C link_to do user_path(5) 'Click here' end

D link_to(user_path(5)) do 'Click here' end

💡 Hint

Blocks in Ruby can be written with do...end or curly braces, but link_to with block usually uses do...end with proper indentation.

Option A correctly uses do...end block syntax with link_to, passing the URL as the first argument and the block returning the link text.

🔧 Debug

advanced

Why does this link_to raise an error?

Given this code:

link_to 'Edit', edit_user_path

Why does it raise an error?

Ruby on Rails

link_to 'Edit', edit_user_path

A edit_user_path is not a valid Rails helper

B link_to requires a block when using edit_user_path

C edit_user_path requires an argument for the user id, but none was given

D link_to cannot use path helpers as the second argument

💡 Hint

Check the method signature of edit_user_path in Rails routes.

The edit_user_path helper expects a user id argument to generate the correct URL. Omitting it causes an ArgumentError.

❓ state_output

advanced

What is the value of the generated URL?

Given this route:

resources :articles

and this code:

article_url(10, host: 'example.com')

What is the full URL generated?

Ruby on Rails

article_url(10, host: 'example.com')

A http://example.com/articles/10

B https://example.com/articles/10

C /articles/10

D http://localhost/articles/10

💡 Hint

article_url generates a full URL including protocol and host.

article_url generates a full URL with http by default and the given host 'example.com'.

🧠 Conceptual

expert

Which option correctly explains polymorphic_url usage?

In Rails, what does polymorphic_url(@comment) do if @comment belongs to a Post?

A Generates the URL for the comment nested under its post, like /posts/:post_id/comments/:id

B Generates the URL for the post only, ignoring the comment

C Raises an error because polymorphic_url cannot handle nested resources

D Generates the URL for the comment only, ignoring its parent post

💡 Hint

Polymorphic helpers build URLs based on the object and its associations.

polymorphic_url(@comment) generates the URL for the comment resource based on its class, like /comments/1. It ignores the parent post unless you pass an array like polymorphic_url([@comment.post, @comment]).

Practice

1. What does the Rails helper link_to primarily do?

easy

A. Generates a plain URL string

B. Creates a clickable HTML link

C. Fetches data from the database

D. Starts a new Rails server

Solution

1. Step 1: Understand the purpose of link_to

   The link_to helper is designed to create clickable links in HTML pages.

2. Step 2: Differentiate from url_for

   Unlike url_for, which returns a URL string, link_to outputs an anchor tag with the link.

3. Final Answer:

   Creates a clickable HTML link -> Option B

4. Quick Check:

   link_to = clickable link [OK]

Hint: Remember: link_to makes links, url_for makes URLs [OK]

Common Mistakes:

• Confusing link_to with url_for
• Thinking link_to fetches data
• Assuming link_to starts server

2. Which of the following is the correct syntax to create a link to the home page with text 'Home' using link_to?

easy

A. link_to 'Home', root_path

B. link_to root_path, 'Home'

C. link_to 'Home' => root_path

D. link_to('Home' root_path)

Solution

1. Step 1: Recall link_to syntax

   The correct syntax is link_to 'Link Text', path_or_url.

2. Step 2: Match options to syntax

   link_to 'Home', root_path matches this pattern exactly. Others have wrong order or syntax errors.

3. Final Answer:

   link_to 'Home', root_path -> Option A

4. Quick Check:

   link_to text, path = link_to 'Home', root_path [OK]

Hint: link_to 'text', path always in that order [OK]

Common Mistakes:

• Swapping arguments order
• Using hash rocket => incorrectly
• Missing comma between arguments

3. What will be the output HTML of this Rails code?

link_to 'Profile', user_path(5), class: 'btn'

medium

A. Profile

B. Profile

C. Profile

D. Profile

Solution

1. Step 1: Understand link_to output

   The link_to helper creates an anchor tag with href set to the URL from user_path(5).

2. Step 2: Check URL and class attribute

   user_path(5) generates "/users/5". The class attribute is added as class="btn".

3. Final Answer:

   <a href="/users/5" class="btn">Profile</a> -> Option C

4. Quick Check:

   link_to with path and class outputs anchor with href and class [OK]

Hint: link_to outputs <a> with href from path helper [OK]

Common Mistakes:

• Forgetting href attribute
• Confusing button tag with link
• Wrong URL path format

4. Identify the error in this code snippet:

link_to 'Edit' edit_user_path user.id

medium

A. Missing parentheses around method argument

B. Incorrect method name, should be edit_user_url

C. link_to requires a block, not arguments

D. Missing comma between arguments

Solution

1. Step 1: Analyze link_to syntax

   The link_to helper requires comma-separated arguments for text and path.

2. Step 2: Check argument separation

   There is no comma between 'Edit' and edit_user_path user.id, causing a syntax error.

3. Final Answer:

   Missing comma between arguments -> Option D

4. Quick Check:

   Arguments must be comma-separated [OK]

Hint: Always separate arguments with commas in helpers [OK]

Common Mistakes:

• Omitting commas between arguments
• Confusing _path and _url helpers
• Thinking link_to needs a block always

5. You want to create a link that opens in a new browser tab with the text 'Docs' linking to https://guides.rubyonrails.org. Which is the correct link_to usage?

hard

A. link_to 'Docs', 'https://guides.rubyonrails.org', target: '_blank', rel: 'noopener'

B. link_to 'Docs', 'https://guides.rubyonrails.org', new_tab: true

C. link_to 'Docs', url_for('https://guides.rubyonrails.org'), open_in_new: true

D. link_to 'Docs', 'https://guides.rubyonrails.org', open: '_new'

Solution

1. Step 1: Identify how to open link in new tab

   In HTML, target="_blank" opens a link in a new tab.

2. Step 2: Add security attribute

   Adding rel="noopener" prevents security risks when opening new tabs.

3. Step 3: Check options syntax

   link_to 'Docs', 'https://guides.rubyonrails.org', target: '_blank', rel: 'noopener' correctly uses target: '_blank' and rel: 'noopener' as options in link_to.

4. Final Answer:

   link_to 'Docs', 'https://guides.rubyonrails.org', target: '_blank', rel: 'noopener' -> Option A

5. Quick Check:

   Use target: '_blank' and rel: 'noopener' for new tab links [OK]

Hint: Use target: '_blank' and rel: 'noopener' for safe new tabs [OK]

Common Mistakes:

• Using non-standard options like new_tab or open_in_new
• Forgetting rel: 'noopener' for security
• Using incorrect target values