Online Booking Tutorial: Ruby

Cronofy’s calendar synchronization and scheduling API enables a rich suite of functionality in any app. Getting started is a quick and straightforward process. This tutorial will guide you through the process of integrating the Cronofy ruby gem into your own application. You’ll see for yourself just how easy it is to check availability and schedule an event.

What we’ll be building #

We’ll create a three-page application that will allow you to connect a calendar account, view your availability, and create a new event.

For page one, we’ll cover the steps necessary to authenticate a new calendar profile and list the connected calendars.

For page two, we’ll make an Availability Query request to view your availability and select a time-slot to book your event.

Finally, in page three, we’ll add the new event to your calendar and display a confirmation.

Before you start #

Creating a new app in the Cronofy dashboard #

Before we can create our own application, we need a Cronofy account to connect to. Log into your account, and navigate to the “Applications” section of the dashboard. There you’ll see the “Create new app” button; clicking this will generate a new application with a new client ID, client secret and SDK Identifier. You’ll need these to authenticate your own app with the Cronofy API, and they can be found on your app’s dashboard page.

Once you have created your application, there will be a prompt for you to authorize access to a calendar. We can skip this step for now because we will be authorizing access to a calendar using the cronofy.get_token_from_code action in Step 2.

Setup your own application #

You’ll also need to setup the scaffolding for your application in whichever language or framework you’re most comfortable with. For this tutorial we’ll be using Ruby on Rails

If you want to follow along with this tutorial, you can download the starter-project here: Developer Demo Ruby repo.

This will provide you with a working Ruby on Rails app; it comes with all the routing already set up for you. Follow the instructions in that repo’s to download the dependencies and start the app server.

For our app, the folder structure will look like this:

  • credentials.yml.enc is an encrypted file where we’ll store our client key and client secret.
  • master.key is a hash string that is used to decrypt the credentials.yml.enc file (This file should NOT be committed to version control).
  • Gemfile stores the information about our Ruby dependencies. Running bundle install after the repo has been downloaded will install all the dependencies.
  • The controllers/ directory is where we will handle our API requests.
  • The views/ directory contains .html.erb templates to provide the markup for each page.

Step 1. Setup the SDK #

We’ll be making use of the cronofy-ruby gem. There are Cronofy SDKs for most major languages, and the concepts covered in this tutorial will apply to whichever language you choose to use.

cronofy-ruby can be installed in your project using bundler. To install, add this line to your applications Gemfile:

gem 'cronofy'

then navigate to the root directory of your project and run this command:

bundle install

This will install the cronofy gem and add the details to the Gemfile.lock.

Once you’ve included the gem, the next step is to add your own credentials (the client ID and client secret we created in the Before you start section) to the credentials.yml.enc file and generate your master.key file. It’s important to keep these credentials secure, and part of that security includes keeping your credentials out of version control. For that reason, we’ve included the both the master.key and credentials.yml.enc files in the .gitignore.

To set your credentials, navigate to the root directory of the project and run rails credentials:edit. This will generate your master.key file and open the credentials.yml.enc file where you can store your credentials like this:

  client_id: CLIENT_ID_GOES_HERE
  client_secret: CLIENT_SECRET_GOES_HERE

We’ve already shown how to find your client_id and client_secret.

The data_center variable is to ensure requests are made to the data center your developer account is linked to. By default, API requests are made to the USA data center. You can find the value for this variable in your app dashboard listed as SDK Identifier.

Now that our credentials are ready to be used, we can start using the Cronofy SDK to make calls to the API.

The ruby SDK does this via the Cronofy::Client class, which we’ll create next. Within the application_controller.rb file, place the following code within the cronofy_client action:

client_id =     Rails.application.credentials[:cronofy][:client_id]
client_secret = Rails.application.credentials[:cronofy][:client_secret]
data_center =   Rails.application.credentials[:cronofy][:data_center]

This will fetch the client_id, client_secret and data_center which we just encrypted into our credentials file, allowing us to use them within our Cronofy::Client.

Next, we will add the following code below the keys to instantiate our new client:
    client_id:     client_id,
    client_secret: client_secret,
    data_center:   data_center

Step 2. The “Home” page #

Now we’ve setup our Cronofy::Client instance, it’s time to put it use. The first page in our application will be our “home” page where we can add and remove connected calendar profiles.

Authorization #

The first step in enabling a user to connect their calendar is to generate a link that will take them through the authorization process. The user will click that link to go through the authorization process and grant access to their calendar. Cronofy uses OAuth2 as a model for much of its authorization. This process will return a code which we will then use to retrieve the ACCESS_TOKEN and sub, using the cronofy.get_token_from_code action.

To generate the link add the following to the index action within the users_controller.rb file:

@cronofy = cronofy_client
@authorization_url = @cronofy.user_auth_link('http://localhost:3000/oauth2/callback')

You will notice that within the config/routes.rb we already have the neccessary routes configured for us.

Then within the views/ directory, open the users/index.html.erb file and replace the "#" of the link_to with @authorization_url.

The next step is to ensure we capture the ACCESS_TOKEN and sub. These tokens will allow us to make requests on behalf of an Account, rather than as our Application, which is how we’ve made our calls so far. To do this, we will add the following code to the connect action within the users_controller.rb file:

@cronofy = cronofy_client()
code = [params[:code]]
response = @cronofy.get_token_from_code(code, 'http://localhost:3000/oauth2/callback')

if User.where(account_id: response.account_id).exists?
    user = User.find_by(account_id: response.account_id)
        access_token: response.access_token,
        refresh_token: response.refresh_token
        user = User.create(
            account_id: response.account_id,
            access_token: response.access_token,
            refresh_token: response.refresh_token

redirect_to root_path

Now if you run rails s from the root directory of your app, and then navigate to http://localhost:3000/ you will be able to see the button to connect a calendar.

Clicking this will send you through the Oauth process and allow you to connect a calendar to your cronofy account.

Viewing the connected calendars #

Now that you have a calendar connected, we can make an API call to List Calendars.

To do this we will first be modifying the client instantiation within the application_controller.rb file. Replace the existing client with the following code:

if user
        client_id:     client_id,
        client_secret: client_secret,
        data_center:   data_center,
        access_token: User.first.access_token,
        refresh_token: User.first.refresh_token
        client_id:     client_id,
        client_secret: client_secret,
        data_center:   data_center

What this allows us to do is offer as much authentication as possible based on whether we are making a request on behalf of the Application or on behalf of an Account.

Next, we will be modifying the code in our index action in users_controller.rb file. We will be making a check to see if there is a User.first so that we can pass it to the cronofy_client and get the relevant client to make the list_calendars call.

We’re going to skip any user management in this tutorial and instead always use User.first. This will help us focus on our interaction with the Cronofy APIs, but you will want to look up the user sub and access token for the user you are acting as (i.e. the currently logged in user).

Find the @cronofy = cronofy_client within the index action of the users_controller.rb file and replace it with the following code:

if User.first
    @cronofy = cronofy_client(User.first)
    @calendars = @cronofy.list_calendars
    @cronofy = cronofy_client
    @calendars = []

In this snippet, we’re deciding if we have a User or not. If we do, we create a Cronofy client for that user and then call the list_calendars method to query the Cronofy list calendars endpoint. The response from this request is wrapped in an object for easier manipulation.

We’ll now use these values to show the calendars on our page.

To view the calendars on the front end, open the users/index.html.erb file within the views/ directory and add in the following code within the card-body div.

<% @calendars.each  do |calendar| %>
<div class="row bg-light border mb-2 p-2">
    <div class="col-auto pt-1"><%= calendar.profile_name %></div>
    <div class="col-auto pt-1"> <%= calendar.provider_name %></div>
    <div class="col-auto">
        <%= link_to 'View availability', calendar_path(calendar.calendar_id), class: "btn btn-secondary" %>
<% end %>

If you refresh your app within your browser window, you will now see the information on the connected calendars. You will notice there is a button to “View Availability”. We will be adding in this functionality in the next step.

Step 3. View your Availablility #

For the second page of our application, we want to be able to view our availability for a set period of time, and to be able to select a time slot to create a new event. We can do this by making an Availability call.

First we will need to do some set up to ensure we have the relevant information available in our show action within our callendars_controller.rb file. Open up this file and place the following code at the top of the show action:

@cronofy = cronofy_client(User.first)
@calendar = [params[:id]]
@duration_minutes = 60

Now we need to construct an availability query.

Constructing an availability query #

In short the availability query is an object that matches a valid Cronofy Availability request. This query defines three things:

  1. The participants that we want to query.
  2. The required duration of the event we want to book.
  3. An array of periods to check availability in.

For this application, our participants object can be relatively simple. We only want to check our own availability, so we only need to add our own profile (using the sub of our account):

participants: [
        required: "all",
        members: [
                sub: sub

The required_duration is set in minutes, and must be greater than zero. It describes the minimum period that a participant must have free for a period to be deemed as available.

query_periods is an array of hashes with a start and end time. Both should be a valid Time data-type, and must represent a future point in time. The end of an available period must also be at least 1 minute after the corresponding start and within 35 days of the earliest start.

For example, to query between 9-10 UTC and 15:00-17:30 UTC, we would set this to:

query_periods: [
        start: "2022-01-20T09:00:00Z",
        end: "2022-01-20T10:00:00Z"
        start: "2022-01-20T15:00:00Z",
        end: "2022-01-20T17:30:00Z"

Your Availability query should eventually look like this:

@request = {
    "participants": [
        "members": [
            "sub": sub
    "response_format": "slots",
    "required_duration": { "minutes": @duration_minutes },
    "available_periods": [
            start: "2022-01-20T09:00:00Z",
            end: "2022-01-20T10:00:00Z"
            start: "2022-01-20T15:00:00Z",
            end: "2022-01-20T17:30:00Z"

Now that we have constructed our availability query we can add the following line to make the call to the API:

@available_periods = @cronofy.availability(@request)

Next we will format the response to view on the front end as selectable slots.

Viewing your availability #

Before we create an event, we need to view the availability on the front end and enable the user to select a slot.

You will notice that in the availability query we just constructed, that we added a response_format with a value of slots. This will generate non-overlapping slots with a length equal to the required_duration.

To view these slots, find the <div class="card-body"></div> within the calendars/show.html.erb file and place the following code inside it:

<%= form_with do |form| %>
<% @available_periods.each do |period| %>
    <div class="d-flex flex-column bg-light border mb-2 pt-1 pl-2">
    <%= label_tag "slot_#{period.start.time.strftime('%Y-%m-%d_%H%M')}" do %>
        <%= form.radio_button :slot, period.start.time.strftime("%Y-%m-%d_%H:%M") %>
        <span><%= period.start.time.strftime("%Y-%m-%d %H:%M") %> - <%= period.end.time.strftime("%H:%M") %></span>
    <% end  %>
<% end  %>
<%= form.hidden_field :duration_minutes, value: @duration_minutes %>
<%= button_to "Create event", { action: "create" }, class: "btn btn-primary" %>
<% end %>

If you now click on the “View Availablility” button on the index page, you should see a page very similar to this:

Cronofy has calculated all of the times our participant is available and returned those times, which we have now displayed on the page.

We are now ready to create an event.

Step 4. Add an event to our calendar #

The last page of our app is where we’ll actually add an event to our calendar. We’re being given the start time in the slot query parameter, and we’ll use the duration_minutes to calculate the end time for our event. We then need to parse that into an object we can use.

Formatting an event #

To add an event to a calendar, we’ll need to create an object that will match the format required by the Create or Update Event section of the API.

In addition to the start and end time, we’ll need to add a unique event_id, a text summary and description, and the calendar_id of the calendar we want to add the event to.

In the calendars_controller.rb file, place the following code within the create action:

@cronofy = cronofy_client(User.first)
calendar_id = params[:id]
start_time = Time.parse(params[:slot])
end_time = start_time + params[:duration_minutes].to_i.minutes

@event_data = {
    event_id: 'uniq-id',
    summary: 'Demo event summary',
    description: 'Demo event description',
    start: start_time,
    end: end_time,
    location: {
        description: "Meeting room"

@cronofy.upsert_event(calendar_id, @event_data)

Now in our application, if you select a slot and click “Create event” you should see a confirmation screen showing you the date and time of the event you just created. You will also see the event created on your calendar.

We’ve completed a full end-to-end journey in our application - we’ve connected the users calendars, made an Availability query and finally created an event in their calendar!

Troubleshooting #

If you encounter unexpected errors at any stage, be sure to check the browser’s console and the command line output.

A common issue is that the access token may have expired, so double check that your access token is fresh. For simplicity this demo app does not handle storing and refreshing of access tokens.

If you have been following along step-by-step in the starter branch of the GitHub repo, try switching to the master branch which includes some basic functionality to refresh your access token.

Next steps