Error messages and display in Ruby on Rails - Mini Project: Build & Apply

Error messages and display

📖 Scenario: You are building a simple Rails web app where users can submit a form to create a new article. You want to show error messages clearly if the user submits invalid data.

🎯 Goal: Create a Rails form for a new Article that shows error messages above the form fields when validation fails.

📋 What You'll Learn

Create an Article model with validations

Add a controller action to handle new article creation

Display error messages in the form view when validations fail

Use Rails helpers to show errors in a user-friendly way

💡 Why This Matters

🌍 Real World

Showing clear error messages in forms is essential for good user experience in web apps. It helps users fix mistakes and submit correct data.

💼 Career

Understanding Rails validations, controller logic, and error display is a core skill for Rails developers building user-friendly web applications.

1

Create the Article model with validations

Create a Rails model called Article with a title attribute that must be present (not blank). Write the validation inside the model file.

Ruby on Rails

# Create Article model with title validation
# Your code here

Need a hint?

Use validates :title, presence: true inside the model class.

2

Add the ArticlesController with new and create actions

Create an ArticlesController with new and create actions. In new, initialize @article = Article.new. In create, build @article = Article.new(article_params) and save it. If save fails, render :new again.

Ruby on Rails

class Article < ApplicationRecord
  validates :title, presence: true
end

# Add ArticlesController with new and create actions
# Your code here

Need a hint?

Remember to permit :title in article_params.

3

Create the form view with error messages display

In the new.html.erb view, create a form for @article using form_with. Above the form fields, add code to display error messages if @article.errors.any?. Show a heading and list each error message inside an unordered list.

Ruby on Rails

class Article 
# Your code here

Need a hint?

Use form_with model: @article, local: true and check @article.errors.any? to show errors.

4

Add flash notice display and final touches

In the application layout or above the form in new.html.erb, add code to display the flash notice if present. Use flash[:notice] inside a div with id notice. This will show success messages after article creation.

Ruby on Rails

class Article 
# Your code here

Need a hint?

Use if flash[:notice] and show it inside a div with id notice.