ERB template syntax in Ruby on Rails - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

Output of ERB expression tags

What will be rendered on the page by this ERB snippet?

<% name = 'Alice' %>
<%= "Hello, #{name}!" %>
<%# This is a comment %>
<% name = 'Bob' %>
<%= "Goodbye, #{name}!" %>

Ruby on Rails

<% name = 'Alice' %>
<%= "Hello, #{name}!" %>
<%# This is a comment %>
<% name = 'Bob' %>
<%= "Goodbye, #{name}!" %>

A Hello, Alice!Goodbye, Bob!

B Hello, Alice!Goodbye, Alice!

C Hello, Bob!Goodbye, Bob!

D Hello, Bob!Goodbye, Alice!

💡 Hint

Remember that <% %> runs Ruby code without output, and <%= %> outputs the result.

The first <% name = 'Alice' %> sets name to 'Alice'. Then <%= "Hello, #{name}!" %> outputs 'Hello, Alice!'. The comment <%# ... %> is ignored. Then name is changed to 'Bob'. The last <%= ... %> outputs 'Goodbye, Bob!'.

📝 Syntax

intermediate

Correct ERB tag for Ruby code without output

Which ERB tag correctly runs Ruby code but does NOT output anything to the page?

A &lt;% ruby_code %&gt;

B &lt;%= ruby_code %&gt;

C &lt;%# ruby_code %&gt;

D &lt;%== ruby_code %&gt;

💡 Hint

Think about which tag runs code silently.

The <% %> tag runs Ruby code but does not output anything. The <%= %> tag outputs the result. The <%# %> is a comment and does not run code. The <%== %> is invalid syntax.

🔧 Debug

advanced

Identify the ERB syntax error

Which option contains an ERB syntax error that will cause the template to fail rendering?

Ruby on Rails

<%= 'Hello' %>
<% if true %>
  <%= 'Yes' %>
<% end %>

A

<% if user_signed_in? %>
<%= 'Welcome!' %>
<% end %>

B

<% if user_signed_in? %>
  <%= 'Welcome!' %>
<% end %>

C

<%= if user_signed_in? %>
  <%= 'Welcome!' %>
<% end %>

D

<% if user_signed_in? %>
  <%== 'Welcome!' %>
<% end %>

💡 Hint

Check which tag is used to start the if statement.

Option C uses <%= if user_signed_in? %> which tries to output the if statement itself, causing a syntax error. The correct way is to use <% if ... %> without = to run code without output.

❓ state_output

advanced

Value of variable after ERB execution

Given this ERB snippet, what is the value of count after rendering?

<% count = 0 %>
<% 3.times do %>
  <% count += 1 %>
<% end %>
<%= count %>

Ruby on Rails

<% count = 0 %>
<% 3.times do %>
  <% count += 1 %>
<% end %>
<%= count %>

A 0

B Error: undefined variable

C 1

D 3

💡 Hint

Remember that Ruby code inside <% %> runs and can change variables.

The variable count starts at 0. The loop runs 3 times, each time adding 1 to count. So count becomes 3. The <%= count %> outputs 3.

🧠 Conceptual

expert

Difference between <%= and <%== in ERB

What is the main difference between the ERB tags <%= %> and <%== %> when rendering HTML content?

A <%= outputs raw HTML without escaping; <%== escapes HTML entities before output

B <%= escapes HTML entities before output; <%== outputs raw HTML without escaping

C Both escape HTML entities before output

D Both output raw HTML without escaping

💡 Hint

Think about safe HTML rendering and escaping.

The <%= %> tag escapes HTML entities to prevent injection attacks, so it outputs safe text. The <%== %> tag outputs raw HTML without escaping, useful when you want to render HTML tags directly.