View helpers in Ruby on Rails - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to use a Rails view helper that creates a link to the home page.

Ruby on Rails

<%= link_to 'Home', [1] %>

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

Ahome_url

Broot_path

Cindex_path

Dmain_page

Attempts:

3 left

💡 Hint

Common Mistakes

Using a URL helper instead of a path helper

Using a non-existent helper name

The root_path helper returns the path to the home page defined in routes.

2fill in blank

medium

Complete the code to safely display user input in a view using a Rails helper.

Ruby on Rails

<%= [1](user_input) %>

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

Araw

Bescape_once

Chtml_safe

Dsanitize

Attempts:

3 left

💡 Hint

Common Mistakes

Using raw which outputs unsafe HTML

Using html_safe on untrusted input

The sanitize helper cleans user input to prevent harmful HTML or scripts.

3fill in blank

hard

Fix the error in the code to correctly display a formatted date using a Rails view helper.

Ruby on Rails

<%= [1](user.created_at, format: :short) %>

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

Aformat_time

Bdate_format

Cl

Dformat_date

Attempts:

3 left

💡 Hint

Common Mistakes

Using non-existent helpers like format_date

Confusing with strftime which is a Ruby method, not a helper

The l helper localizes and formats dates and times according to Rails conventions.

4fill in blank

hard

Fill both blanks to create a form input field with a label using Rails view helpers.

Ruby on Rails

<%= [1] :user, :email %>
<%= [2] :user, :email %>

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

Alabel

Btext_field

Cemail_field

Dform_for

Attempts:

3 left

💡 Hint

Common Mistakes

Using text_field instead of email_field for email inputs

Mixing up the order of label and input helpers

The label helper creates a label tag, and email_field creates an input for email.

5fill in blank

hard

Fill all three blanks to create a link that opens in a new tab with Rails view helpers.

Ruby on Rails

<%= link_to [1], [2], [3]: '_blank' %>

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

A'Google'

B'https://www.google.com'

Ctarget

Drel

Attempts:

3 left

💡 Hint

Common Mistakes

Using rel instead of target for opening in new tabs

Not quoting the link text or URL

The first argument is the link text, the second is the URL, and the third is the option key target to open in a new tab.

Practice

1. What is the main purpose of view helpers in Rails?

easy

A. To handle database queries and data storage

B. To generate HTML or text for views in a clean and reusable way

C. To manage user sessions and authentication

D. To configure routes and URL patterns

Solution

1. Step 1: Understand the role of view helpers

   View helpers are Ruby methods designed to create HTML or text snippets for views, making the code cleaner and reusable.

2. Step 2: Differentiate from other Rails components

   Helpers do not handle database, sessions, or routing; those are handled by models, controllers, and routes respectively.

3. Final Answer:

   To generate HTML or text for views in a clean and reusable way -> Option B

4. Quick Check:

   View helpers = generate HTML/text [OK]

Hint: Helpers create HTML/text for views, not data or routes [OK]

Common Mistakes:

• Confusing helpers with models or controllers
• Thinking helpers manage database or sessions
• Assuming helpers configure routes

2. Which of the following is the correct way to use a Rails view helper in an ERB template?

easy

A. <%= link_to 'Home', root_path %>

B. <% link_to 'Home', root_path %>

C. <%= link_to 'Home', 'root_path' %>

D. <%== link_to 'Home', root_path %>

Solution

1. Step 1: Identify correct ERB syntax for output

   To display the result of a helper method, use <%= ... %> which outputs the returned HTML.

2. Step 2: Check the helper usage

   link_to 'Home', root_path correctly calls the helper with a path helper method, not a string.

3. Final Answer:

   <%= link_to 'Home', root_path %> -> Option A

4. Quick Check:

   Use <%= ... %> to output helper results [OK]

Hint: Use <%= ... %> to output helper results in ERB [OK]

Common Mistakes:

• Using <% ... %> which does not output content
• Passing path as a string instead of method
• Using <%== ... %> which is for raw HTML, not needed here

3. Given this helper method in app/helpers/application_helper.rb:

def greeting(name)
  "Hello, #{name}!"
end

What will this ERB code output?

<%= greeting('Alice') %>

medium

A. Hello, Alice!

B. greeting('Alice')

C. Hello, name!

D. Error: undefined method 'greeting'

Solution

1. Step 1: Understand the helper method behavior

   The method greeting takes a name and returns the string "Hello, #{name}!" with the name inserted.

2. Step 2: Evaluate the ERB output

   The ERB tag <%= greeting('Alice') %> calls the method with 'Alice' and outputs the returned string.

3. Final Answer:

   Hello, Alice! -> Option A

4. Quick Check:

   Helper returns string with name inserted [OK]

Hint: Helpers return strings; <%= ... %> outputs them [OK]

Common Mistakes:

• Thinking it outputs the method call as text
• Confusing variable interpolation syntax
• Assuming helper is undefined if not included

4. You wrote this helper method:

def format_price(price)
  "$#{price.round(2)}"
end

But in your view, calling <%= format_price(5) %> shows an error: NoMethodError: undefined method 'round' for 5:Integer. What is the problem?

medium

A. You must call round with parentheses: round(2)

B. Helpers cannot use Ruby methods like round

C. The dollar sign should be escaped as \$

D. Integer does not have a round method; convert to float first

Solution

1. Step 1: Understand the error message

   The error says Integer (5) has no method 'round', which is true because round is a Float method.

2. Step 2: Fix the method to convert price to float

   Convert price to float before calling round, e.g., price.to_f.round(2), so rounding works.

3. Final Answer:

   Integer does not have a round method; convert to float first -> Option D

4. Quick Check:

   round works on floats, not integers [OK]

Hint: Use to_f before round to avoid Integer errors [OK]

Common Mistakes:

• Assuming round works on integers
• Thinking parentheses cause the error
• Believing helpers can't use Ruby methods

5. You want to create a helper that generates a list of user names as an unordered HTML list. Which helper method implementation correctly returns safe HTML for this in Rails?

hard

A. def user_list(users)
users.each { |u| "#{u.name}" }
end

B. def user_list(users)
"" + users.map { |u| "#{u.name}" }.join + ""
end

C. def user_list(users)
content_tag(:ul) do
users.map { |u| content_tag(:li, u.name) }.join.html_safe
end
end

D. def user_list(users)
content_tag(:ul, users.map { |u| content_tag(:li, u.name) })
end

Solution

1. Step 1: Understand safe HTML generation in helpers

   content_tag with a block correctly wraps the list items in <ul> tags, and joining with html_safe marks the string safe.

2. Step 2: Analyze each option

   def user_list(users) content_tag(:ul) do users.map { |u| content_tag(:li, u.name) }.join.html_safe end end uses content_tag with block and html_safe join, which is correct. def user_list(users) "
   " + users.map { |u| "
   • #{u.name}
   " }.join + "
   " end returns a string but lacks html_safe, risking unsafe output. def user_list(users) users.each { |u| "
3. #{u.name}
" } end returns an array, not a string. def user_list(users) content_tag(:ul, users.map { |u| content_tag(:li, u.name) }) end passes an array as content_tag content, which renders incorrectly.

4. Final Answer:

   def user_list(users) content_tag(:ul) do users.map { |u| content_tag(:li, u.name) }.join.html_safe end end -> Option C

5. Quick Check:

   Use content_tag with block and html_safe join [OK]

Hint: Use content_tag with block and join(...).html_safe for lists [OK]

Common Mistakes:

• Returning raw strings without html_safe
• Passing arrays directly to content_tag content
• Using each instead of map for generating list items