Why views present data in Ruby on Rails

Introduction

Views show data to users in a clear and friendly way. They turn raw information into pages people can read and understand.

When you want to display a list of products on a webpage.

When showing user profile details like name and email.

When presenting search results after a user submits a query.

When you need to format dates or numbers nicely for users.

When you want to separate how data looks from how it is stored or processed.

Syntax

Ruby on Rails

<%= @variable %>

Use <%= %> to insert Ruby data into HTML in a view.

Instance variables like @variable come from the controller.

Examples

Shows the user's name inside a heading.

Ruby on Rails

<h1>Welcome, <%= @user.name %>!</h1>

Displays the current date formatted nicely.

Ruby on Rails

<p>Today is <%= Date.today.strftime('%B %d, %Y') %>.</p>

Loops through items and shows each title in a list.

Ruby on Rails

<ul>
  <% @items.each do |item| %>
    <li><%= item.title %></li>
  <% end %>
</ul>

Sample Program

This example shows a controller setting a message, and the view displaying it inside a paragraph.

Ruby on Rails

# app/controllers/welcome_controller.rb
class WelcomeController < ApplicationController
  def index
    @message = "Hello, Rails learner!"
  end
end

# app/views/welcome/index.html.erb
<h1>Message for you:</h1>
<p><%= @message %></p>

Important Notes

Views should only display data, not change it.

Keep logic in controllers or helpers, not in views.

Use partials to reuse view code and keep things tidy.

Summary

Views turn data into readable pages for users.

They use special tags to insert Ruby data into HTML.

Controllers prepare data, views present it clearly.

Practice

1. Why do views in Rails present data to users?

easy

A. To store data in the database

B. To turn raw data into readable web pages

C. To handle user login and authentication

D. To manage server configuration settings

Solution

1. Step 1: Understand the role of views in MVC

   Views are responsible for showing data to users in a readable format, usually as HTML pages.

2. Step 2: Differentiate views from other parts

   Controllers prepare data, models handle data storage, but views present data clearly to users.

3. Final Answer:

   To turn raw data into readable web pages -> Option B

4. Quick Check:

   Views present data = To turn raw data into readable web pages [OK]

Hint: Views display data as pages, not store or process it [OK]

Common Mistakes:

• Confusing views with controllers or models
• Thinking views handle data storage
• Assuming views manage server settings

2. Which of the following is the correct way to insert Ruby data into a Rails view using ERB syntax?

easy

A. <% @user.name %>

B. [[ @user.name ]]

C. {{ @user.name }}

D. <%= @user.name %>

Solution

1. Step 1: Identify ERB syntax for output

   In Rails views, <%= %> outputs Ruby code result into HTML.

2. Step 2: Compare options

   <% %> runs Ruby code but does not output it; {{ }} and [[ ]] are not Rails ERB syntax.

3. Final Answer:

   <%= @user.name %> -> Option D

4. Quick Check:

   ERB output tag = <%= @user.name %> [OK]

Hint: Use <%= %> to show Ruby data in views [OK]

Common Mistakes:

• Using <% %> which does not output data
• Confusing with other template syntaxes like {{ }}
• Forgetting to use equals sign for output

3. Given the controller sets @items = ['apple', 'banana', 'cherry'], what will this view code output?

<ul>
  <% @items.each do |item| %>
    <li><%= item.upcase %></li>
  <% end %>
</ul>

medium

A. APPLEBANANACHERRY

B. applebananacherry

C. ItemItemItem

D. Syntax error due to missing output tag

Solution

1. Step 1: Understand the loop and method

   The code loops over @items and outputs each item in uppercase inside <li> tags.

2. Step 2: Check output tags and method

   <%= item.upcase %> outputs the uppercase string; the loop is correct.

3. Final Answer:

   <ul><li>APPLE</li><li>BANANA</li><li>CHERRY</li></ul> -> Option A

4. Quick Check:

   Loop with upcase output =
   • APPLE
   • BANANA
   • CHERRY
   [OK]

Hint: Look for <%= %> to output transformed data inside loop [OK]

Common Mistakes:

• Confusing <% %> with <%= %> causing no output
• Ignoring the upcase method effect
• Assuming original lowercase output

4. Identify the error in this Rails view snippet:

<ul>
  <% @products.each do |product| %>
    <li><%= product.name %></li>
  <% end %>
</ul>

medium

A. No error, code is correct

B. Using <%= inside <% block without closing properly

C. Incorrect ERB output tag syntax

D. Missing closing tag for <li>

Solution

1. Step 1: Inspect ERB tags inside the loop

   The code uses proper ERB syntax: <% %> for the loop, <%= product.name %> for output, and HTML tags correctly placed.

2. Step 2: Verify no syntax issues

   All tags are properly opened and closed; no mixing of ERB and HTML incorrectly.

3. Final Answer:

   No error, code is correct -> Option A

4. Quick Check:

   Valid Rails ERB view code = No error, code is correct [OK]

Hint: Ensure ERB tags <%= %> wrap only Ruby code, not HTML [OK]

Common Mistakes:

• Placing HTML closing bracket inside ERB tag
• Confusing <% and <%= tags
• Assuming no syntax error when mixing tags

5. You want to display a list of users with their email only if the email is present. Which view code correctly presents this conditional data?

<ul>
  <% @users.each do |user| %>
    <li>
      <%= user.name %>
      <% if user.email.present? %>
        (<%= user.email %>)
      <% end %>
    </li>
  <% end %>
</ul>

hard

A. Syntax error due to missing output tags

B. Always shows email even if empty

C. Correctly shows name and email only if email exists

D. Does not loop through users properly

Solution

1. Step 1: Analyze the loop and conditional

   The code loops over @users and shows user.name always.

2. Step 2: Check conditional email display

   The if condition checks if email is present, then outputs it inside parentheses.

3. Step 3: Verify ERB syntax correctness

   Output tags <%= %> are used properly for name and email; control flow tags <% %> for condition.

4. Final Answer:

   Correctly shows name and email only if email exists -> Option C

5. Quick Check:

   Conditional display with correct ERB = Correctly shows name and email only if email exists [OK]

Hint: Use <% if %> for conditions, <%= %> to output data [OK]

Common Mistakes:

• Using <%= for if without closing properly
• Outputting email without checking presence
• Forgetting to close loop or condition tags