Firebase Cloud Messaging (FCM) for Android and iOS

The FCM gem lets your ruby backend send notifications to Android and iOS devices via Firebase Cloud Messaging.

Installation

$ gem install fcm

or in your Gemfile just include it:

gem 'fcm'

Requirements

For Android you will need a device running 2.3 (or newer) that also have the Google Play Store app installed, or an emulator running Android 2.3 with Google APIs. iOS devices are also supported.

A version of supported Ruby, currently: ruby >= 2.4

Getting Started

To use this gem, you need to instantiate a client with your firebase credentials:

fcm = FCM.new(
  GOOGLE_APPLICATION_CREDENTIALS_PATH,
  FIREBASE_PROJECT_ID
)

About the `GOOGLE_APPLICATION_CREDENTIALS_PATH`

The GOOGLE_APPLICATION_CREDENTIALS_PATH is meant to contain your firebase credentials.

The easiest way to provide them is to pass here an absolute path to a file with your credentials:

fcm = FCM.new(
  '/path/to/credentials.json',
  FIREBASE_PROJECT_ID
)

As per their secret nature, you might not want to have them in your repository. In that case, another supported solution is to pass a StringIO that contains your credentials:

fcm = FCM.new(
  StringIO.new(ENV.fetch('FIREBASE_CREDENTIALS')),
  FIREBASE_PROJECT_ID
)

Usage

HTTP v1 API

To migrate to HTTP v1 see: https://firebase.google.com/docs/cloud-messaging/migrate-v1

fcm = FCM.new(
  GOOGLE_APPLICATION_CREDENTIALS_PATH,
  FIREBASE_PROJECT_ID
)
message = {
  'token': "000iddqd", # send to a specific device
  # 'topic': "yourTopic",
  # 'condition': "'TopicA' in topics && ('TopicB' in topics || 'TopicC' in topics)",
  'data': {
    payload: {
      data: {
        id: 1
      }
    }.to_json
  },
  'notification': {
    title: notification.title_th,
    body: notification.body_th,
  },
  'android': {},
  'apns': {
    payload: {
      aps: {
        sound: "default",
        category: "#{Time.zone.now.to_i}"
      }
    }
  },
  'fcm_options': {
    analytics_label: 'Label'
  }
}

fcm.send_v1(message) # or fcm.send_notification_v1(message)

Device Group Messaging

With device group messaging, you can send a single message to multiple instance of an app running on devices belonging to a group. Typically, "group" refers a set of different devices that belong to a single user. However, a group could also represent a set of devices where the app instance functions in a highly correlated manner. To use this feature, you will first need an initialised FCM class.

The maximum number of members allowed for a notification key is 20. https://firebase.google.com/docs/cloud-messaging/android/device-group#managing_device_groups

Generate a Notification Key for device group

Then you will need a notification key which you can create for a particular key_name which needs to be uniquely named per app in case you have multiple apps for the same project_id. This ensures that notifications only go to the intended target app. The create method will do this and return the token notification_key, that represents the device group, in the response:

project_id is the SENDER_ID in your cloud settings. https://firebase.google.com/docs/cloud-messaging/concept-options#senderid

params = { key_name: "appUser-Chris",
                project_id: "my_project_id",
                registration_ids: ["4", "8", "15", "16", "23", "42"] }
response = fcm.create(*params.values)

Send to Notification device group

To send messages to device groups, use the HTTP v1 API, Sending messages to a device group is very similar to sending messages to an individual device, using the same method to authorize send requests. Set the token field to the group notification key

message = {
  'token': "NOTIFICATION_KEY", # send to a device group
  # ...data
}

fcm.send_v1(message)

Add/Remove Registration Tokens

You can also add/remove registration Tokens to/from a particular notification_key of some project_id. For example:

params = { key_name: "appUser-Chris",
                project_id: "my_project_id",
                notification_key:"appUser-Chris-key",
                registration_ids:["7", "3"] }
response = fcm.add(*params.values)

params = { key_name: "appUser-Chris",
                project_id: "my_project_id",
                notification_key:"appUser-Chris-key",
                registration_ids:["8", "15"] }
response = fcm.remove(*params.values)

Send Messages to Topics

FCM topic messaging allows your app server to send a message to multiple devices that have opted in to a particular topic. Based on the publish/subscribe model, one app instance can be subscribed to no more than 2000 topics. Sending to a topic is very similar to sending to an individual device or to a user group, in the sense that you can use the fcm.send_v1 method where the topic matches the regular expression "/topics/[a-zA-Z0-9-_.~%]+":

message = {
  'topic': "yourTopic", # send to a device group
  # ...data
}

fcm.send_v1(message)

Or you can use the fcm.send_to_topic helper:

response = fcm.send_to_topic("yourTopic",
            notification: { body: "This is a FCM Topic Message!"} )

Send Messages to Topics with Conditions

FCM topic condition messaging to send a message to a combination of topics, specify a condition, which is a boolean expression that specifies the target topics.

message = {
  'condition': "'TopicA' in topics && ('TopicB' in topics || 'TopicC' in topics)", # send to topic condition
  # ...data
}

fcm.send_v1(message)

Or you can use the fcm.send_to_topic_condition helper:

response = fcm.send_to_topic_condition(
  "'TopicA' in topics && ('TopicB' in topics || 'TopicC' in topics)",
  notification: {
    body: "This is an FCM Topic Message sent to a condition!"
  }
)

Sending to Multiple Topics

To send to combinations of multiple topics, require that you set a condition key to a boolean condition that specifies the target topics. For example, to send messages to devices that subscribed to TopicA and either TopicB or TopicC:

'TopicA' in topics && ('TopicB' in topics || 'TopicC' in topics)

FCM first evaluates any conditions in parentheses, and then evaluates the expression from left to right. In the above expression, a user subscribed to any single topic does not receive the message. Likewise, a user who does not subscribe to TopicA does not receive the message. These combinations do receive it:

TopicA and TopicB
TopicA and TopicC

You can include up to five topics in your conditional expression, and parentheses are supported. Supported operators: &&, ||, !. Note the usage for !:

!('TopicA' in topics)

With this expression, any app instances that are not subscribed to TopicA, including app instances that are not subscribed to any topic, receive the message.

The send_to_topic_condition method within this library allows you to specicy a condition of multiple topics to which to send to the data payload.

response = fcm.send_to_topic_condition(
  "'TopicA' in topics && ('TopicB' in topics || 'TopicC' in topics)",
  notification: {
    body: "This is an FCM Topic Message sent to a condition!"
  }
)

Given a registration token and a topic name, you can add the token to the topic using the Google Instance ID server API.

topic = "YourTopic"
registration_token= "12" # a client registration token
response = fcm.topic_subscription(topic, registration_token)
# or unsubscription
response = fcm.topic_unsubscription(topic, registration_token)

Or you can manage relationship maps for multiple app instances Google Instance ID server API. Manage relationship

topic = "YourTopic"
registration_tokens= ["4", "8", "15", "16", "23", "42"] # an array of one or more client registration tokens
response = fcm.batch_topic_subscription(topic, registration_tokens)
# or unsubscription
response = fcm.batch_topic_unsubscription(topic, registration_tokens)

Get Information about the Instance ID

Given a registration token, you can retrieve information about the token using the Google Instance ID server API.

registration_token= "12" # a client registration token
response = fcm.get_instance_id_info(registration_token)

To get detailed information about the instance ID, you can pass an optional options hash to the get_instance_id_info method:

registration_token= "12" # a client registration token
options = { "details" => true }
response = fcm.get_instance_id_info(registration_token, options)

Mobile Clients

You can find a guide to implement an Android Client app to receive notifications here: Set up a FCM Client App on Android.

The guide to set up an iOS app to get notifications is here: Setting up a FCM Client App on iOS.

ChangeLog

2.0.0

Breaking Changes

Remove deprecated API_KEY
Remove deprecated send method
Remove deprecated send_with_notification_key method
Remove subscribe_instance_id_to_topic method
Remove unsubscribe_instance_id_from_topic method
Remove batch_subscribe_instance_ids_to_topic method
Remove batch_unsubscribe_instance_ids_from_topic method

Supported Features

Add HTTP v1 API support for send_to_topic_condition method
Add HTTP v1 API support for send_to_topic method

1.0.8

caches calls to Google::Auth::ServiceAccountCredentials #103
Allow faraday versions from 1 up to 2 #101

1.0.7

Fix passing DEFAULT_TIMEOUT to faraday #96
Fix issue with get_instance_id_info option params #98
Accept any IO object for credentials #95

Huge thanks to @excid3 @jsparling @jensljungblad

1.0.3

Fix overly strict faraday dependency

1.0.2

Bug fix: retrieve notification key" params: https://github.com/spacialdb/fcm/commit/b328a75c11d779a06d0ceda83527e26aa0495774

1.0.0

Bumped supported ruby to >= 2.4
Fix deprecation warnings from faraday by changing dependency version to faraday 1.0.0

0.0.7

replace httparty with faraday

0.0.2

Fixed group messaging url.
Added API to recover_notification_key.

0.0.1

Initial version.

MIT License

Many thanks to all the contributors

Contributors

Cutting a release

Update version in fcm.gemspec with VERSION and update README.md ## ChangeLog section.

# set the version
# VERSION="1.0.7"
gem build fcm.gemspec
git tag -a v${VERSION} -m "Releasing version v${VERSION}"
git push origin --tags
gem push fcm-${VERSION}.gem