How to Use Checkbox in Form Rails in Ruby on Rails

In Ruby on Rails, use the check_box helper inside a form builder to add a checkbox input. It automatically handles the checked and unchecked states and submits the value to the controller for processing.

Syntax

The check_box helper is used inside a form builder like form_with or form_for. It takes the attribute name and optional options.

• attribute: The model attribute linked to the checkbox.
• options: Hash for HTML options like checked, disabled, or class.
• checked_value: Value submitted when checked (default is "1").
• unchecked_value: Value submitted when unchecked (default is "0").

erb

<%= form_with model: @user do |form| %>
  <%= form.check_box :subscribe_newsletter, {}, "yes", "no" %>
  <%= form.label :subscribe_newsletter, "Subscribe to newsletter" %>
<% end %>

Example

This example shows a form with a checkbox for a User model's subscribe_newsletter boolean attribute. When the form is submitted, the controller receives "yes" if checked or "no" if unchecked.

ruby+erb

# app/views/users/_form.html.erb
<%= form_with model: @user do |form| %>
  <div>
    <%= form.label :subscribe_newsletter, "Subscribe to newsletter" %>
    <%= form.check_box :subscribe_newsletter, {}, "yes", "no" %>
  </div>
  <div>
    <%= form.submit "Save" %>
  </div>
<% end %>

# app/controllers/users_controller.rb
class UsersController < ApplicationController
  def new
    @user = User.new
  end

  def create
    @user = User.new(user_params)
    if @user.save
      redirect_to @user, notice: "User created successfully."
    else
      render :new
    end
  end

  private

  def user_params
    params.require(:user).permit(:subscribe_newsletter)
  end
end

Output

Rendered form with a checkbox labeled 'Subscribe to newsletter'. When checked, the form submits subscribe_newsletter: "yes"; when unchecked, it submits "no".

Common Pitfalls

One common mistake is forgetting that unchecked checkboxes do not send any value by default, which can cause the attribute to be nil instead of false. Rails solves this by sending a hidden field with the unchecked_value. Another pitfall is not permitting the checkbox attribute in strong parameters, causing it to be ignored.

Also, avoid manually adding a hidden field for unchecked values; the check_box helper does this automatically.

erb

<!-- Wrong: Missing unchecked value, checkbox may not submit false -->
<%= form.check_box :subscribe_newsletter %>

<!-- Right: Rails adds hidden field automatically -->
<%= form.check_box :subscribe_newsletter, {}, "1", "0" %>

Quick Reference

Usage	Description
form.check_box :attribute	Creates a checkbox linked to model attribute with default values (checked: "1", unchecked: "0")
form.check_box :attribute, {}, "yes", "no"	Checkbox with custom checked and unchecked values
params.require(:model).permit(:attribute)	Permit checkbox attribute in controller strong parameters
form.label :attribute, "Label text"	Adds a label for the checkbox for accessibility

Key Takeaways

Use the Rails form builder's check_box helper to add checkboxes linked to model attributes.

Always permit the checkbox attribute in strong parameters to allow its value through.

Rails automatically adds a hidden field to handle unchecked checkboxes, so do not add it manually.

Customize checked and unchecked values by passing them as arguments to the check_box helper.

Use labels with checkboxes for better accessibility and user experience.