Action methods in Ruby on Rails - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What does this Rails controller action render?

Consider this Rails controller action:

def show
  @user = User.find(params[:id])
end

What will this action render by default when called?

A It renders the template 'show.html.erb' inside the 'users' folder automatically.

B It renders plain text with the user's name.

C It redirects to the index action of the controller.

D It raises an error because no render or redirect is specified.

💡 Hint

Rails automatically renders a view matching the action name unless told otherwise.

In Rails, if an action does not explicitly call render or redirect, it automatically renders the template matching the action name in the controller's view folder.

❓ state_output

intermediate

What is the value of @message after this action runs?

Given this Rails controller action:

def greet
  @message = params[:name] || 'Guest'
end

If the URL is '/greet?name=Alice', what is the value of @message?

A An error is raised because params[:name] is a string

B 'Alice'

C nil

D 'Guest'

💡 Hint

Check if params[:name] exists and what value it holds.

Since the URL provides 'name=Alice', params[:name] is 'Alice', so @message is set to 'Alice'.

📝 Syntax

advanced

Which option correctly defines a Rails action that redirects to root path?

You want an action named 'home' that redirects users to the root path. Which code is correct?

A

def home
  redirect root_path
end

B

def home
  render root_path
end

C

def home
  redirect_to root_path
end

D

def home
  redirect_to :root
end

💡 Hint

Look for the correct Rails method to redirect and the correct argument.

'redirect_to' is the correct method to redirect, and 'root_path' is the helper for the root URL.

🔧 Debug

advanced

Why does this action raise an error?

Examine this Rails controller action:

def update
  @post = Post.find(params[:id])
  @post.update(params[:post])
  redirect_to @post
end

Why might this code raise an error?

A params[:post] is not permitted, causing a ForbiddenAttributesError.

B Post.find(params[:id]) returns nil, causing a NoMethodError.

C redirect_to @post is invalid syntax and causes a syntax error.

D update method does not exist on ActiveRecord objects.

💡 Hint

Check how Rails handles strong parameters for mass assignment.

Rails requires strong parameters to permit attributes for update. Passing params[:post] directly causes a ForbiddenAttributesError.

🧠 Conceptual

expert

Which statement about Rails action methods is true?

Select the correct statement about action methods in Rails controllers.

A Action methods must always explicitly call render or redirect_to to produce a response.

B Private methods in controllers can be used as actions if called via routes.

C Action methods run only once when the server starts, then cache their output.

D Action methods can access params and instance variables to pass data to views.

💡 Hint

Think about how data flows from controller to view in Rails.

Action methods have access to params and can set instance variables that views use to display data.