Link and URL helpers in Ruby on Rails - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the link_to helper do in Rails?

The link_to helper creates an HTML anchor (<a>) tag that links to a specified URL or path. It helps generate clickable links easily in views.

beginner

How do you generate a URL for a named route in Rails?

You use URL helpers that Rails creates from your routes, like posts_path or post_url(@post). These helpers return the path or full URL for the route.

intermediate

What is the difference between _path and _url helpers in Rails?

_path helpers return a relative path (like /posts/1), while _url helpers return the full URL including the domain (like http://example.com/posts/1).

intermediate

How can you add HTML options like CSS classes or data attributes to a link_to helper?

You pass a hash of HTML options as the last argument to <code>link_to</code>. For example, <code>link_to 'Home', root_path, class: 'nav-link', data: { toggle: 'dropdown' }</code> adds a class and data attribute.

intermediate

What helper would you use to create a link that submits a DELETE request in Rails?

Use link_to with the method: :delete option. Rails uses JavaScript to convert the link click into a DELETE HTTP request.

Which helper generates a clickable link in Rails?

A link_to

B url_for

C form_for

D button_to

link_to creates clickable links. url_for generates URLs but not links.

What does posts_path return?

A Full URL including domain

B JavaScript code

C Relative path like '/posts'

D HTML anchor tag

posts_path returns the relative path for posts.

How do you add a CSS class to a link_to helper?

A Use <code>class</code> key in options hash

B Pass class name as second argument

C Wrap link_to in a <code>&lt;div&gt;</code>

D Add class in controller

You add HTML options like class using a hash as the last argument.

Which option makes link_to send a DELETE request?

A method: :get

B method: :delete

C method: :post

D method: :put

method: :delete tells Rails to send a DELETE HTTP request.

What is the difference between post_path(@post) and post_url(@post)?

A No difference

B <code>post_path</code> returns full URL, <code>post_url</code> returns path

C One is for GET, other for POST

D <code>post_path</code> returns path, <code>post_url</code> returns full URL

post_path returns relative path; post_url returns full URL with domain.

Explain how to create a link in Rails that looks like a button and sends a DELETE request when clicked.

Think about link_to options and styling.

Describe the difference between URL helpers ending with _path and those ending with _url in Rails.

Consider what the browser needs to navigate.

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