View helpers in Ruby on Rails - Mini Project: Build & Apply

Using View Helpers in Rails

📖 Scenario: You are building a simple Rails app that shows a list of books with their titles and authors. You want to keep your views clean by using a view helper to format the book display.

🎯 Goal: Create a view helper method that formats a book's title and author, then use it in the view to display each book nicely.

📋 What You'll Learn

Create a helper method called formatted_book that takes a book object

The helper should return a string combining the book's title and author in this format: "Title by Author"

Use the formatted_book helper method inside the view to display each book

Ensure the view iterates over a list of books and calls the helper for each

💡 Why This Matters

🌍 Real World

View helpers are used in Rails apps to keep HTML views simple and reusable by moving formatting logic to helper methods.

💼 Career

Knowing how to write and use view helpers is essential for Rails developers to build maintainable and accessible web applications.

1

Set up the books data

Create a variable called @books in the controller with an array of hashes. Each hash should have keys :title and :author with these exact values: { title: 'The Hobbit', author: 'J.R.R. Tolkien' } and { title: '1984', author: 'George Orwell' }.

Ruby on Rails

# Create @books array with two hashes for books
# Your code here

Hint

Use an array of hashes assigned to @books in your controller.

2

Add a view helper method

In the helper file, define a method called formatted_book that takes one parameter book. It should return a string combining the book's title and author in this exact format: "Title by Author" using string interpolation.

Ruby on Rails

# Define formatted_book helper method here
# Your code here

Hint

Use string interpolation inside the helper method to combine title and author.

3

Use the helper in the view

In the view file, write a for loop that iterates over @books with the variable book. Inside the loop, call the helper method formatted_book(book) to display each book's formatted string inside a <li> element.

Ruby on Rails

   -->
  # Your code here

Hint

Use ERB tags to embed Ruby code and call the helper inside the loop.

4

Add accessibility and semantic HTML

Wrap the list in a <section> with an aria-label attribute set to "Book list". This helps screen readers understand the content. Add this attribute to the existing <ul> or its container.

Ruby on Rails

# Your code here

Hint

Use semantic <section> and add aria-label for accessibility.

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