Stimulus and Turbo (Hotwire) in Ruby on Rails - Mini Project: Build & Apply

Build a Simple Like Button with Stimulus and Turbo

📖 Scenario: You are creating a small interactive feature for a blog post page. Readers can click a like button to increase the like count without reloading the page.This uses Stimulus to handle the button click and Turbo to update the like count dynamically.

🎯 Goal: Build a like button that increments the like count on click using Stimulus controller and Turbo frame updates.

📋 What You'll Learn

Create a Turbo Frame with a unique ID to wrap the like count

Create a Stimulus controller named like to handle button clicks

Add a data-action to the button to call the Stimulus controller method

Update the like count inside the Turbo Frame without full page reload

💡 Why This Matters

🌍 Real World

This pattern is common in modern Rails apps to create fast, interactive UI elements without full page reloads, improving user experience.

💼 Career

Understanding Stimulus and Turbo is essential for Rails developers building responsive, real-time features efficiently.

1

Set up the Turbo Frame and initial like count

Create a Turbo Frame tag with id="like_count_frame" that contains a span showing the initial like count of 0.

Ruby on Rails

  0

Hint

Use the <turbo-frame> tag with the exact id="like_count_frame" and put a <span> inside showing 0.

2

Add the Stimulus controller and button

Add a button with data-controller="like" and data-action="click->like#increment". The button text should be Like.

Ruby on Rails

  0

like#increment">Like

Hint

Add a <button> with the exact data-controller="like" and data-action="click->like#increment" attributes and text 'Like'.

3

Create the Stimulus controller with increment method

Create a Stimulus controller named like_controller.js with an increment method that fetches the Turbo Frame with id="like_count_frame" and updates its inner span by increasing the number by 1.

Ruby on Rails

// app/javascript/controllers/like_controller.js
import { Controller } from "@hotwired/stimulus"

export default class extends Controller {
  increment() {
    // Your code here
  }
}

Hint

Inside increment(), get the element with id="like_count_frame", find the span, read its number, add 1, and update the text.

4

Connect Stimulus controller in HTML and finalize

Ensure the Stimulus controller is loaded by adding data-controller="like" to the button and that the Turbo Frame and button are inside the same HTML snippet. Confirm the button click updates the like count inside the Turbo Frame.

Ruby on Rails

  0

like#increment">Like

// app/javascript/controllers/like_controller.js
import { Controller } from "@hotwired/stimulus"

export default class extends Controller {
  increment() {
    const frame = document.getElementById("like_count_frame")
    const span = frame.querySelector("span")
    const currentCount = Number(span.textContent)
    span.textContent = currentCount + 1
  }
}

# Confirm the Stimulus controller is connected and working
# Your code here

Hint

Make sure the button has data-controller="like" and data-action="click->like#increment" and the Turbo Frame is present in the HTML.

Practice

1. What is the main purpose of Stimulus in a Rails application using Hotwire?

easy

A. To add simple JavaScript behavior to HTML elements using controllers and data attributes

B. To replace the entire page content on every user action

C. To handle database queries efficiently

D. To style HTML elements with CSS

Solution

1. Step 1: Understand Stimulus role

   Stimulus is designed to add JavaScript behavior to HTML by connecting controllers to elements via data attributes.

2. Step 2: Compare other options

   Replacing entire page content is Turbo's job, not Stimulus. Database queries and styling are unrelated.

3. Final Answer:

   To add simple JavaScript behavior to HTML elements using controllers and data attributes -> Option A

4. Quick Check:

   Stimulus = JavaScript behavior via controllers [OK]

Hint: Stimulus controls behavior, Turbo controls page updates [OK]

Common Mistakes:

• Confusing Turbo's page update role with Stimulus
• Thinking Stimulus handles styling or database
• Assuming Stimulus reloads full pages

2. Which of the following is the correct way to connect a Stimulus controller named hello to a button element?

easy

A. Click me

B. Click me

C. Click me

D. Click me

Solution

1. Step 1: Recall Stimulus controller connection syntax

   Stimulus controllers are connected using the data-controller attribute with the controller name.

2. Step 2: Verify other attributes

   data-action defines event handlers, data-target defines targets inside controllers, data-connect is invalid.

3. Final Answer:

   <button data-controller="hello">Click me</button> -> Option B

4. Quick Check:

   Controller connection uses data-controller [OK]

Hint: Use data-controller to link Stimulus controllers [OK]

Common Mistakes:

• Using data-action instead of data-controller to connect controller
• Confusing data-target with controller connection
• Using non-existent data-connect attribute

3. Given this Stimulus controller code:

export default class extends Controller {
  static targets = ["output"]
  greet() {
    this.outputTarget.textContent = "Hello, Stimulus!"
  }
}

and this HTML:

<div data-controller="greeting">
  <button data-action="click->greeting#greet">Say Hello</button>
  <span data-greeting-target="output"></span>
</div>

What happens when the button is clicked?

medium

A. The span text changes to 'Hello, Stimulus!'

B. Nothing happens because the controller name is wrong

C. The page reloads

D. An error is thrown because outputTarget is undefined

Solution

1. Step 1: Match controller and targets

   The controller is named 'greeting' and defines an output target. The HTML uses data-controller="greeting" and data-greeting-target="output" correctly.

2. Step 2: Understand the greet method and action

   The button triggers greet on click, which sets the outputTarget's textContent to 'Hello, Stimulus!'.

3. Final Answer:

   The span text changes to 'Hello, Stimulus!' -> Option A

4. Quick Check:

   Correct controller and target update text [OK]

Hint: Check controller name matches data-controller and targets [OK]

Common Mistakes:

• Mismatching controller name and data-controller attribute
• Forgetting to define static targets array
• Expecting page reload instead of DOM update

4. Identify the error in this Turbo Frame usage:

<turbo-frame id="messages">
  <%= render @messages %>
</turbo-frame>

When a new message is created, the frame does not update automatically. What is the likely cause?

medium

A. The frame id should be messages_frame instead of messages

B. Turbo Frames cannot render collections

C. The render call is missing a partial

D. The server response does not include a turbo-frame with matching id

Solution

1. Step 1: Understand Turbo Frame update mechanism

   Turbo Frames update only if the server response includes a turbo-frame element with the same id as the frame on the page.

2. Step 2: Identify the problem

   If the server response lacks a matching turbo-frame wrapper, Turbo cannot replace the frame content automatically.

3. Final Answer:

   The server response does not include a <turbo-frame> with matching id -> Option D

4. Quick Check:

   Matching turbo-frame id in response is required [OK]

Hint: Ensure server response wraps content in matching turbo-frame id [OK]

Common Mistakes:

• Changing frame id arbitrarily
• Assuming Turbo Frames can't render collections
• Forgetting to wrap response in turbo-frame tag

5. You want to create a live search feature using Turbo and Stimulus. Which approach correctly combines both to update search results as the user types without full page reload?

hard

A. Use Stimulus to reload the whole page manually on input change

B. Use Turbo Frames alone to reload the entire page on every keystroke

C. Use a Stimulus controller to listen for input events, send fetch requests to the server, and update a Turbo Frame with the results

D. Use Turbo Streams to replace the entire page content on input

Solution

1. Step 1: Understand live search requirements

   Live search updates results dynamically as the user types without full reload.

2. Step 2: Combine Stimulus and Turbo correctly

   Stimulus listens to input events and sends fetch requests. Turbo Frame updates only the results part of the page.

3. Step 3: Evaluate other options

   Reloading entire page on every keystroke is inefficient. Turbo Streams replace parts but need server push. Stimulus alone can't reload page efficiently.

4. Final Answer:

   Use a Stimulus controller to listen for input events, send fetch requests to the server, and update a Turbo Frame with the results -> Option C

5. Quick Check:

   Stimulus + Turbo Frame = dynamic partial updates [OK]

Hint: Stimulus handles events, Turbo Frame updates partial content [OK]

Common Mistakes:

• Reloading full page on every input
• Using Turbo Frames without Stimulus for input events
• Misusing Turbo Streams for full page replacement