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Steve Polito
Steve Polito

Posted on • Edited on • Originally published at stevepolito.design

Automatically Unsubscribe from Emails in Rails (and Control Email Preferences)

#tutorial #rails

In this tutorial, I'll show you how to add a link to any Rails Mailer that will allow a user to automatically unsubscribe from that email. As an added bonus, we'll build a page allowing a user to update their email preferences across all mailers.

Inspired by GoRails.

demo

Step 1: Build Mailers

  1. Generate mailers. 
rails g mailer marketing promotion rails g mailer notification notify
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  1. Update previews by passing a user into the mailer. This assumes your database has at least one user record. 
# test/mailers/previews/marketing_mailer_preview.rb class MarketingMailerPreview < ActionMailer::Preview def promotion MarketingMailer.with( user: User.first, ... ).promotion end end
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# test/mailers/previews/notification_mailer_preview.rb class NotificationMailerPreview < ActionMailer::Preview def notify NotificationMailer.with( user: User.first ... ).notify end end
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Step 2: Build a Model to Save Email Preferences

  1. Generate the model and migration. 
rails g model mailer_subscription user:references subscribed:boolean mailer:string
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  1. Add a null constraint to the mailer column, and a unique index on the user_id and mailer columns. This will prevent duplicate records. 
class CreateMailerSubscriptions < ActiveRecord::Migration[6.1] def change create_table :mailer_subscriptions do |t| t.references :user, null: false, foreign_key: true t.boolean :subscribed t.string :mailer, null: false t.timestamps end add_index(:mailer_subscriptions, [:user_id, :mailer], unique: true) end end
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What's Going On Here?

  • We add null: false to the mailer column to prevent empty values from being saved, since this column is required.
  • We add a unique index on the user_id and mailer columns to prevent a user from having multiple preferences for a mailer.
  1. Run the migrations. 
rails db:migrate
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  1. Build the MailerSubscription model. 
# app/models/mailer_subscription.rb class MailerSubscription < ApplicationRecord belongs_to :user MAILERS = OpenStruct.new( items: [ { class: "MarketingMailer", name: "Marketing Emails", description: "Updates on promotions and sales." }, { class: "NotificationMailer", name: "Notification Emails", description: "Notifications from the website." } ] ).freeze validates :subscribed, inclusion: [true, false], allow_nil: true validates :mailer, presence: true validates :mailer, inclusion: MAILERS.items.map{ |item| item[:class] } validates :user, uniqueness: { scope: :mailer } # @mailer_subscription.details # => [{:class => "MarketingMailer", :name => "Marketing Emails", :description => "Updates on promotions and sales."}] def details MailerSubscription::MAILERS.items.select {|item| item[:class] == mailer } end # @mailer_subscription.name # => "Marketing Emails" def name details[0][:name] end # @mailer_subscription.name # => "Updates on promotions and sales." def description details[0][:description] end # @mailer_subscription.name # => "Subscribe to" def action subscribed? ? "Unsubscribe from" : "Subscribe to" end # @mailer_subscription.name # => "Subscribe to Marketing Emails" def call_to_action "#{action} #{name}" end end
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What's Going On Here

  • We add a constant to store a list of mailers a user will be able to subscribe/unsubscribe from. The class value must match the name of a Mailer class.
  • We use the values stored in the constant to constrain what values can be set on the mailer column. This prevents us from accidentally creating a record with an invalid mailer.
  • We add a uniqueness validator between the user and mailer. This is made possible by the unique index we created in the migration. This will ensure a user cannot have multiple preferences for the same mailer.
  • We use the values stored in the constant to create a variety of helper methods that can be used in views.
  1. Add method to check if a user is subscribed to a specific mailer. 
# app/models/user.rb class User < ApplicationRecord has_many :mailer_subscriptions, dependent: :destroy # @user.subscribed_to_mailer? "MarketingMailer" # => true def subscribed_to_mailer?(mailer) MailerSubscription.find_by( user: self, mailer: mailer, subscribed: true ).present? end end
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What's Going On Here?

  • We add a method that checks if a user is subscribed to a particular mailer. If the method finds a matching record, then the user is subscribed. Otherwise, they are not. Note that this is an opt-in strategy. We're deliberately looking for records where subscribed is set to true. This means that if there is no record in the database, they'll be considered unsubscribed.
  • To make this an opt-out strategy, you could simply replace subscribed: true with subscribed: false.

Step 3: Allow a User to Automatically Unsubscribe from a Mailer

  1. Generate a controller to handle automatic unsubscribes. 
rails g controller mailer_subscription_unsubcribes
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# config/routes.rb Rails.application.routes.draw do ... resources :mailer_subscription_unsubcribes, only: [:show, :update] end
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  1. Build the endpoints. 
# app/controllers/mailer_subscription_unsubcribes_controller.rb class MailerSubscriptionUnsubcribesController < ApplicationController before_action :set_user, only: [:show, :update] before_action :set_mailer_subscription, only: [:show, :update] def show if @mailer_subscription.update(subscribed: false) @message = "You've successfully unsubscribed from this email." else @message = "There was an error" end end def update if @mailer_subscription.toggle!(:subscribed) redirect_to root_path, notice: "Subscription updated." else redirect_to root_path, notice: "There was an error." end end private def set_user @user = GlobalID::Locator.locate_signed params[:id] @message = "There was an error" if @user.nil? end def set_mailer_subscription @mailer_subscription = MailerSubscription.find_or_initialize_by( user: @user, mailer: params[:mailer] ) end end
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  1. Build the view. 
<%# app/views/mailer_subscription_unsubcribes/show.html.erb %> <h1>Unsubscribe</h1> <p><%= @message %></p> <%= button_to @mailer_subscription.call_to_action, mailer_subscription_unsubcribe_path, method: :patch, params: { mailer: params[:mailer] } if @mailer_subscription.present? %>
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You can test this be getting the Global ID of a user and going to the endpoint.

User.first.to_sgid.to_s # => "abc123..."
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http://localhost:3000/mailer_subscription_unsubcribes/abc123...?mailer=MarketingMailer

Page where a user can auto unsubscribe from mailer

What's Going On Here?

  • We create an endpoint that will automatically unsubscribe a user from a particular mailer. This is a little unconventional since we're creating a record on a GET request (instead of a POST request). We're forced to do this because a user will be clicking a link from an email to unsubscribe. If emails supported forms, we could create a POST request.
  • We add a button on that page that will allow the user to resubscribe to the mailer. Note that we don't redirect back to the show action because that would end up unsubscribing the user from the mailer again.
  • We find the user through their GlobalID in the URL which makes the URLs difficult to discover. Otherwise the URL would just accept the user's ID which is much easier to guess. This will prevent a bad actor from from unsubscribing a user from a mailer.

Step 4: Build a Page for User to Update Their Email Preferences

  1. Generate a controller for the MailerSubscription model. 
rails g controller mailer_subscriptions
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# config/routes.rb Rails.application.routes.draw do ... resources :mailer_subscription_unsubcribes, only: [:show, :update] resources :mailer_subscriptions, only: [:index, :create, :update] end
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  1. Build the endpoints. 
# app/controllers/mailer_subscriptions_controller.rb class MailerSubscriptionsController < ApplicationController before_action :authenticate_user! before_action :set_mailer_subscription, only: :update before_action :handle_unauthorized, only: :update def index @mailer_subscriptions = MailerSubscription::MAILERS.items.map do |item| MailerSubscription.find_or_initialize_by(mailer: item[:class], user: current_user) end end def create @mailer_subscription = current_user.mailer_subscriptions.build(mailer_subscription_params) @mailer_subscription.subscribed = true if @mailer_subscription.save redirect_to mailer_subscriptions_path, notice: "Preferences updated." else redirect_to mailer_subscriptions_path, alter: "#{@mailer_subscription.errors.full_messages.to_sentence}" end end def update if @mailer_subscription.toggle!(:subscribed) redirect_to mailer_subscriptions_path, notice: "Preferences updated." else redirect_to mailer_subscriptions_path, alter: "#{@mailer_subscription.errors.full_messages.to_sentence}" end end private def mailer_subscription_params params.require(:mailer_subscription).permit(:mailer) end def set_mailer_subscription @mailer_subscription = MailerSubscription.find(params[:id]) end def handle_unauthorized redirect_to root_path, status: :unauthorized, notice: "Unauthorized." and return if current_user != @mailer_subscription.user end end
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What's Going On Here?

  • We create a page allowing a user to subscribe/unsubscribe from all possible mailers that are defined in MailerSubscription::MAILERS. We can't call @user.mailer_subscriptions because they may not have any records.
  • We create a handle_unauthorized method to prevent a user from subscribing/unsubscribing another user from mailers. We need to do this because we're passing in the ID of the MailerSubscription through the params hash which can be altered via the browser.
  1. Build the views. 
<%# app/views/mailer_subscriptions/index.html.erb %> <ul style="list-style:none;"> <%= render @mailer_subscriptions %> </ul>
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<%# app/views/mailer_subscriptions/_mailer_subscription.html.erb %> <% if mailer_subscription.new_record? %> <li style="margin-bottom: 16px;"> <p><%= mailer_subscription.description %></p> <%= button_to mailer_subscriptions_path, params: { mailer_subscription: mailer_subscription.attributes } do %> <%= mailer_subscription.call_to_action %> <% end %> <hr/> </li> <% else %> <li style="margin-bottom: 16px;"> <p><%= mailer_subscription.description %></p> <%= button_to mailer_subscription_path(mailer_subscription), method: :put do %> <%= mailer_subscription.call_to_action %> <% end %> <hr/> </li> <% end %>
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What's Going On Here?

  • We loop through each MailerSubscription instance. If it's a new_record? we create a MailerSubscription. Otherwise, it's an existing record and we toggle! the subscribed value.
  • In either case we use a button_to to hit the correct endpoint. Note that when we're creating a new MailerSubscription we pass mailer_subscription.attributes as params, but we're only permitting the mailer value in our controller.

http://localhost:3000/mailer_subscriptions

Page for User to Update Their Email Preferences

Step 5: Add Unsubscribe Link to Mailer and Prevent Delivery if User Has Unsubscribed

  1. Add shared logic to ApplicationMailer. 
# app/mailers/application_mailer.rb class ApplicationMailer < ActionMailer::Base before_action :set_user before_action :set_unsubscribe_url, if: :should_unsubscribe? before_action :set_mailer_subscriptions_url, if: :should_unsubscribe? after_action :prevent_delivery_if_recipient_opted_out, if: :should_unsubscribe? default from: 'from@example.com' layout 'mailer' private def prevent_delivery_if_recipient_opted_out mail.perform_deliveries = @user.subscribed_to_mailer? self.class.to_s end def set_user @user = params[:user] end def set_unsubscribe_url @unsubscribe_url = mailer_subscription_unsubcribe_url(@user.to_sgid.to_s, mailer: self.class) end def set_mailer_subscriptions_url @mailer_subscriptions_url = mailer_subscriptions_url end def should_unsubscribe? @user.present? && @user.respond_to?(:subscribed_to_mailer?) end end
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What's Going On Here?

  • We add several action mailer callbacks to the ApplicationMailer in order for this logic to be shared across all mailers.
  • We call prevent_delivery_if_recipient_opted_out which will conditionally prevent the mailer from being sent if the user is not subscribed to that mailer. This is accomplished by setting mail.perform_deliveries to true or false based on the return value of @user.subscribed_to_mailer? self.class.to_s. Note that calling self.class.to_s will return the name of the mailer (i.e. MarketingMailer).
  • We call @user.to_sgid.to_s to ensure the the URL is unique and does not contain the user's id. Otherwise a bad actor could unsubscribe any user from a mailer.
  • We conditionally call these callbacks with should_unsubscribe? to ensures we've passed a user to the mailer.
  1. Conditionally render unsubscribe links in mailer layouts. 
<%# app/views/layouts/mailer.html.erb %> <!DOCTYPE html> <html> ... <body> <%= yield %> <%= render "shared/mailers/unsubscribe_links" if @unsubscribe_url.present? %> </body> </html>
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<%# app/views/layouts/mailer.txt.erb %> <%= yield %> <%= render "shared/mailers/unsubscribe_links" if @unsubscribe_url.present? %>
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Conditionally render unsubscribe links in mailer layouts.

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