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The easiest way to write a Slack bot in Ruby.

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Slack-Ruby-Bot

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Warning: As of December 4th, 2020 Slack no longer accept resubmissions from apps that are not using granular permissions, or so-called "classic apps". On November 18, 2021 Slack will start delisting apps that have not migrated to use granular permissions. This library implements legacy, real-time support for classic apps. You should not be building a new bot with it and use slack-ruby-bot-server-events instead. For a rudimentary bot you can even start with slack-ruby-bot-server-events-app-mentions. See MIGRATION for migration help.

The slack-ruby-bot library is a generic Slack bot framework written in Ruby on top of slack-ruby-client. This library does all the heavy lifting, such as message parsing, so you can focus on implementing slack bot commands. It also attempts to introduce the bare minimum number of requirements or any sorts of limitations. It's a Slack bot boilerplate.

If you are not familiar with Slack bots or Slack API concepts, you might want to watch this video.

Table of Contents

Useful to Me?

  • If you are just trying to send messages to Slack, use slack-ruby-client, which this library is built on top of.
  • If you're trying to roll out a full service with Slack button integration, check out slack-ruby-bot-server, which uses this library.
  • Otherwise, this piece of the puzzle will help you create a single bot instance for one team.

Stable Release

You're reading the documentation for the next release of slack-ruby-bot. Please see the documentation for the last stable release, v0.16.1 unless you're integrating with HEAD. See CHANGELOG for a history of changes and UPGRADING for how to upgrade to more recent versions.

Usage

A Minimal Bot

Gemfile

source 'https://rubygems.org'

gem 'slack-ruby-bot'
gem 'async-websocket', '~>0.8.0'

pongbot.rb

require 'slack-ruby-bot'

class PongBot < SlackRubyBot::Bot
  command 'ping' do |client, data, match|
    client.say(text: 'pong', channel: data.channel)
  end
end

PongBot.run

After registering the bot, run with SLACK_API_TOKEN=... bundle exec ruby pongbot.rb. Have the bot join a channel and send it a ping.

A Production Bot

A typical production Slack bot is a combination of a vanilla web server and a websocket application that talks to the Slack Real Time Messaging API. See our Writing a Production Bot tutorial for more information.

More Involved Examples

The following examples of bots based on slack-ruby-bot are listed in growing order of complexity.

Commands and Operators

Bots are addressed by name, they respond to commands and operators. You can combine multiple commands.

class CallBot < SlackRubyBot::Bot
  command 'call', '呼び出し' do |client, data, match|
    client.say(channel: data.channel, text: 'called')
  end
end

Command match data includes match['bot'], match['command'] and match['expression']. The bot match always checks against the SlackRubyBot::Config.user and SlackRubyBot::Config.user_id values obtained when the bot starts.

The command method can take strings, which will have to be escaped with Regexp.escape, and regular expressions.

class CallBot < SlackRubyBot::Bot
  command 'string with spaces', /some\s*regex+\?*/ do |client, data, match|
    client.say(channel: data.channel, text: match['command'])
  end
end

Operators are 1-letter long and are similar to commands. They don't require addressing a bot nor separating an operator from its arguments. The following class responds to =2+2.

class MathBot < SlackRubyBot::Bot
  operator '=' do |client, data, match|
    # implementation detail
  end
end

Operator match data includes match['operator'] and match['expression']. The bot match always checks against the SlackRubyBot::Config.user setting.

Threaded Messages

To reply to a message in a thread you must provide a reference to the first message that initiated the thread, which is available as either data.ts if no threaded messages have been sent, or data.thread_ts if the message being replied to is already in a thread. See message-threading for more information.

command 'reply in thread' do |client, data, match|
  client.say(
    channel: data.channel,
    text: "let's avoid spamming everyone, I will tell you what you need in this thread",
    thread_ts: data.thread_ts || data.ts
  )
end

Note that sending a message using only thread_ts: data.ts can cause some permanent issues where Slack will keep reporting inaccessible messages as unread. At the time of writing the slack team is still having problems clearing those notifications. As recommended by the slack documentation ...

A true parent's thread_ts should be used when replying. Providing a child's message ID will result in a new, detached thread breaking all context and sense.

... the replies to a thread should always be sent to the message ts that started the thread, available as thread_ts for subsequent messages. Hence data.thread_ts || data.ts.

For additional options, including broadcasting, see slack-ruby-client#chat_postMessage.

Bot Aliases

A bot will always respond to its name (eg. rubybot) and Slack ID (eg. @rubybot), but you can specify multiple aliases via the SLACK_RUBY_BOT_ALIASES environment variable or via an explicit configuration.

SLACK_RUBY_BOT_ALIASES=:pp: table-tennis

SlackRubyBot.configure do |config|
  config.aliases = [':pong:', 'pongbot']
end

Bots will also respond to a direct message, with or without the bot name in the message itself.

Generic Routing

Commands and operators are generic versions of bot routes. You can respond to just about anything by defining a custom route.

class Weather < SlackRubyBot::Bot
  match /^How is the weather in (?<location>\w*)\?$/ do |client, data, match|
    client.say(channel: data.channel, text: "The weather in #{match[:location]} is nice.")
  end
end

You can also capture multiple matchers with scan.

class Market < SlackRubyBot::Bot
  scan(/([A-Z]{2,5})/) do |client, data, stocks|
    # lookup stock market price
  end
end

See examples/market for a working example.

Matching text in message attachments

You can respond to text in attachments with attachment. It will scan text, pretext and title fields in each attachment until a first match is found.

For example you can match this example attachment by its title with the following bot:

class Attachment < SlackRubyBot::Bot
  attachment 'Slack API Documentation' do |client, data, match|
    client.say(channel: data.channel, text: "Matched by #{match.attachment_field}.")
    client.say(channel: data.channel, text: "The attachment's text: #{match.attachment.text}.")
  end
end

You can also define which fields in attachment object should be scanned.

Scan only a single field:

class Attachment < SlackRubyBot::Bot
  attachment 'Slack API Documentation', :title do |client, data, match|
    # implementation details
  end
end

Scan multiple fields:

class Attachment < SlackRubyBot::Bot
  attachment 'Slack API Documentation', %i[text pretext author_name] do |client, data, match|
    # implementation details
  end
end

Providing description for your bot and commands

You can specify help information for bot or commands with help block, for example:

in case of bot:

class WeatherBot < SlackRubyBot::Bot
  help do
    title 'Weather Bot'
    desc 'This bot tells you the weather.'

    command 'clouds' do
      desc 'Tells you how many clouds there\'re above you.'
    end

    command 'What\'s the weather in <city>?' do
      desc 'Tells you the weather in a <city>.'
      long_desc "Accurate 10 Day Weather Forecasts for thousands of places around the World.\n" \
        'Bot provides detailed Weather Forecasts over a 10 day period updated four times a day.'
    end
  end

  # commands implementation
end

in case of your own command:

class Deploy < SlackRubyBot::Commands::Base
  help do
    title 'deploy'
    desc 'deploys your app'
    long_desc 'command format: *deploy <branch> to <env>* where <env> is production or staging'
  end
end

Customize your command help output

If you've used the help block described above to document your commands, you can provide your own implementation of outputting help for commands like so:

class Market < SlackRubyBot::Bot
  command 'help' do |client, data, match|
    user_command = match[:expression]
    help_attrs = SlackRubyBot::Commands::Support::Help.instance.find_command_help_attrs(user_command)
    client.say(channel: data.channel, text: "#{help_attrs.command_desc}\n\n#{help_attrs.command_long_desc}")
  end
end

SlackRubyBot::Commands::Base

The SlackRubyBot::Bot class is DSL sugar deriving from SlackRubyBot::Commands::Base. For more involved bots you can organize the bot implementation into subclasses of SlackRubyBot::Commands::Base manually. By default a command class responds, case-insensitively, to its name. A class called Phone that inherits from SlackRubyBot::Commands::Base responds to phone and Phone and calls the call method when implemented.

class Phone < SlackRubyBot::Commands::Base
  command 'call'

  def self.call(client, data, match)
    client.say(channel: data.channel, text: 'called')
  end
end

To respond to custom commands and to disable automatic class name matching, use the command keyword. The following command responds to call and 呼び出し (call in Japanese).

class Phone < SlackRubyBot::Commands::Base
  command 'call'
  command '呼び出し'

  def self.call(client, data, match)
    client.say(channel: data.channel, text: 'called')
  end
end

Authorization

The framework does not provide any user authentication or command authorization capability out of the box. However, the SlackRubyBot::Commands::Base class does check every command invocation for permission prior to executing the command. The default method always returns true.

Therefore, subclasses of SlackRubyBot::Commands::Base can override the permitted? private method to provide its own authorization logic. This method is intended to be exploited by user code or external gems that want to provide custom authorization logic for command execution.

class AuthorizedBot < SlackRubyBot::Commands::Base
  command 'phone home' do |client, data, match|
    client.say(channel: data.channel, text: 'Elliot!')
  end

  # Only allow user 'Uxyzabc' to run this command
  def self.permitted?(client, data, match)
    data && data.user && data.user == 'Uxyzabc'
  end
end

Built-In Commands

Slack-ruby-bot comes with several built-in commands. You can re-define built-in commands, normally, as described above.

[bot name]

This is also known as the default command. Shows bot version and links.

[bot name] hi

Politely says 'hi' back.

[bot name] help

Get help.

Hooks

Hooks are event handlers and respond to Slack RTM API events, such as hello or message. You can implement your own in a couple of ways:

Implementing and registering a Hook Handler

A Hook Handler is any object that respond to a call message, like a proc, instance of an object, class with a call class method, etc.

Hooks can be registered using different methods based on user preference / use case. Currently someone can use one of the following methods:

  • Pass hooks in SlackRubyBot::Server initialization.
  • Register hooks on SlackRubyBot::Server using on class method.
  • Register hooks on SlackRubyBot::Server using on instance method.
Hooks registration on SlackRubyBot::Server initialization
SlackRubyBot::Server.new(hook_handlers: {
  hello: MyBot::Hooks::UserChange.new,
  user_change: [->(client, data) {  }, ->(client, data) {}]
})
Hooks registration on a SlackRubyBot::Server instance
# Register an object that implements `call` method
class MyBot::Hooks::Hello
  def call(client, data)
    puts "Hello"
  end
end

server.on(:hello, MyBot::Hooks::Hello.new)

# or register a lambda function to handle the event
server.on(:hello, ->(client, data) { puts "Hello!" })

For example, the following hook handles user_change, an event sent when a team member updates their profile or data. This can be useful to update the local user cache when a user is renamed.

module MyBot
  module Hooks
    class UserChange
      def call(client, data)
        # data['user']['id'] contains the user ID
        # data['user']['name'] contains the new user name
        # ...
      end
    end
  end
end
Hooks registration on SlackRubyBot::Server class

Example:

module MyBot
  class MyServer < SlackRubyBot::Server
    on 'hello' do |client, data|
      # data['user']['id'] contains the user ID
      # data['user']['name'] contains the new user name
    end

    on 'user_change', ->(client, data) {
      # data['user']['id'] contains the user ID
      # data['user']['name'] contains the new user name
    }
  end
end

These will get pushed into the hook set on initialization.

Either by configuration, explicit assignment or hook blocks, multiple handlers can exist for the same event type.

Bot Message Protection

By default bots do not respond to self or other bots. If you wish to change that behavior globally, set allow_bot_messages to true.

SlackRubyBot.configure do |config|
  config.allow_bot_messages = true
end

Message Loop Protection

By default bots do not respond to their own messages. If you wish to change that behavior globally, set allow_message_loops to true.

SlackRubyBot.configure do |config|
  config.allow_message_loops = true
end

Logging

By default bots set a logger to $stdout with DEBUG level. The logger is used in both the RealTime and Web clients.

Silence logger as follows.

SlackRubyBot::Client.logger.level = Logger::WARN

If you wish to customize logger, set logger to your logger.

SlackRubyBot.configure do |config|
  config.logger = Logger.new("slack-ruby-bot.log", "daily")
end

Advanced Integration

You may want to integrate a bot or multiple bots into other systems, in which case a globally configured bot may not work for you. You may create instances of SlackRubyBot::Server which accepts token and aliases.

EM.run do
  bot1 = SlackRubyBot::Server.new(token: token1, aliases: ['bot1'])
  bot1.start_async

  bot2 = SlackRubyBot::Server.new(token: token2, aliases: ['bot2'])
  bot2.start_async
end

For an example of advanced integration that supports multiple teams, see slack-gamebot and playplay.io that is built on top of it.

Proxy Configuration

There are several proxy options that can be configured on Slack::Web::Client. You can also control what proxy options are used by modifying the http_proxy environment variable per Net::HTTP's documentation.

Note that Docker on OSX seems to incorrectly set the proxy, causing Faraday::ConnectionFailed, ERROR -- : Failed to open TCP connection to : (getaddrinfo: Name or service not known). You might need to manually unset http_proxy in that case, eg. http_proxy="" bundle exec ruby ./my_bot.rb.

Model-View-Controller Design

The command method is essentially a controller method that receives input from the outside and acts upon it. Complex behaviors could lead to a long and difficult-to-understand command block. A complex command block is a candidate for separation into classes conforming to the Model-View-Controller pattern popularized by Rails.

The library provides three helpful base classes named SlackRubyBot::MVC::Model::Base, SlackRubyBot::MVC::View::Base, and SlackRubyBot::MVC::Controller::Base.

Testing a command block is difficult. As separate classes, the Model/View/Controller's behavior can be tested via rspec or a similar tool.

Controller

The Controller is the focal point of the bot behavior. Typically the code that would go into the command block will now go into an instance method in a Controller subclass. The instance method name should match the command name exactly (case sensitive).

As an example, these two classes are functionally equivalent.

Consider the following Agent class which is the simplest default approach to take.

class Agent < SlackRubyBot::Bot
  command 'sayhello', 'alternate way to call hello' do |client, data, match|
    client.say(channel: data.channel, text: "Received command #{match[:command]} with args #{match[:expression]}")
  end
end

Using the MVC functionality, we would create a controller instead to encapsulate this function.

class MyController < SlackRubyBot::MVC::Controller::Base
  def sayhello
    client.say(channel: data.channel, text: "Received command #{match[:command]} with args #{match[:expression]}")
  end
  alternate_name :sayhello, :alternate_way_to_call_hello
end
MyController.new(MyModel.new, MyView.new)

Note in the above example that the Controller instance method sayhello does not receive any arguments. When the instance method is called, the Controller class sets up some accessor methods to provide the normal client, data, and match objects. These are the same objects passed to the command block.

However, the Controller anticipates that the model and view objects should contain business logic that will also operate on the client, data, and match objects. The controller provides access to the model and view via the model and view accessor methods. The inventory example provides a full example of a Model, View, and Controller working together.

A Controller may need helper methods for certain work. To prevent the helper method from creating a route that the bot will respond to directly, the instance method name should begin with an underscore (e.g. _my_helper_method). When building the bot routes, these methods will be skipped.

Calling alternate_name after the method definition allows for method aliases similar to the regular command structure. When commands can be triggered by multiple text strings it's useful to have that ability map to the controller methods too.

Lastly, the Controller class includes ActiveSupport::Callbacks which allows for full flexibility in creating before, after, and around hooks for all methods. Again, see the inventory example for more information.

Model

A complex bot may need to read or write data from a database or other network resource. Setting up and tearing down these connections can be costly, so the model can do it once upon instantiation.

The Model also includes ActiveSupport::Callbacks.

class MyModel < SlackRubyBot::MVC::Model::Base
  define_callbacks :sanitize
  set_callback :sanitize, :around, :sanitize_resource
  attr_accessor :_resource

  def initialize
    @db = setup_database_connection
  end

  def read(resource)
    self._resource = resource
    run_callbacks :sanitize do
      @db.select(:column1 => resource)
      # ... do some expensive work
    end
  end

  private

  def sanitize_resource
    self._resource.downcase
    result = yield
    puts "After read, result is #{result.inspect}"
  end
end

Like Controllers, the Model is automatically loaded with the latest version of the client, data, and match objects each time the controller method is called. Therefore the model will always have access to the latest objects when doing its work. It will typically only use the data and match objects.

Model methods are not matched to routes, so there is no restriction on how to name methods as there is in Controllers.

View

A typical bot just writes to a channel or uses the web client to react/unreact to a message. More complex bots will probably require more complex behaviors. These should be stored in a SlackRubyBot::MVC::View::Base subclass.

class MyView < SlackRubyBot::MVC::View::Base
  define_callbacks :logit
  set_callbacks :logit, :around, :audit_trail

  def initialize
    @mailer = setup_mailer
    @ftp = setup_ftp_handler
  end

  def email_admin(message)
    run_callbacks :logit do
      @mailer.send(:administrator, message)
    end
  end

  def react_thumbsup
    client.web_client.reactions_add(
      name: :thumbsup,
      channel: data.channel,
      timestamp: data.ts,
      as_user: true)
  end

  def react_thumbsdown
    client.web_client.reactions_remove(
      name: :thumbsup,
      channel: data.channel,
      timestamp: data.ts,
      as_user: true)
  end

  private

  def audit_trail
    Logger.audit("Sending email at [#{Time.now}]")
    yield
    Logger.audit("Email sent by [#{Time.now}]")
  end
end

Again, the View will have access to the most up to date client, data, and match objects. It will typically only use the client and data objects.

View methods are not matched to routes, so there is no restriction on how to name methods as there is in Controllers.

Testing

RSpec Shared Behaviors

Slack-ruby-bot comes with a number of shared RSpec behaviors that can be used in your RSpec tests.

Require slack-ruby-bot/rspec in your spec_helper.rb along with the following dependencies in Gemfile.

group :development, :test do
  gem 'rack-test'
  gem 'rspec'
  gem 'vcr'
  gem 'webmock'
end

Use the respond_with_slack_message matcher.

describe SlackRubyBot::Commands do
  it 'responds with any message' do
    expect(message: "#{SlackRubyBot.config.user} hi").to respond_with_slack_message
  end
  it 'says hi' do
    expect(message: "#{SlackRubyBot.config.user} hi").to respond_with_slack_message('hi')
  end
end

Use the respond_with_slack_messages matcher for multiple messages.

describe SlackRubyBot::Commands do
  it 'responds with more than one message' do
    expect(message: "#{SlackRubyBot.config.user} count").to respond_with_slack_messages
  end
  it 'says one and two' do
    expect(message: "#{SlackRubyBot.config.user} count").to respond_with_slack_messages(['one', 'two'])
  end
end

Message matchers support regular expressions.

describe SlackRubyBot::Commands do
  it 'says hi' do
    expect(message: "#{SlackRubyBot.config.user} hi").to respond_with_slack_message(/hi/)
  end
end

Check that the bot called client.start_typing(channel: 'channel').

describe SlackRubyBot::Commands do
 it 'starts typing on channel' do
    expect(message: "#{SlackRubyBot.config.user} hi").to start_typing(channel: 'channel')
  end
end

Testing Lower Level Messages

You can test client behavior at a lower level by fetching the message hook. The following example expects a bot command to call client.typing(channel: data.channel).

describe SlackRubyBot::Commands do
  let(:app) { Server.new }
  let(:client) { app.send(:client) }
  let(:message_hook) { SlackRubyBot::Hooks::Message.new }
  it 'receives a typing event' do
      expect(client).to receive(:typing)
      message_hook.call(
        client,
        Hashie::Mash.new(text: "#{SlackRubyBot.config.user} type something", channel: 'channel')
      )
    end
  end
end

Useful Libraries

Contributing

See CONTRIBUTING.

Upgrading

See CHANGELOG for a history of changes and UPGRADING for how to upgrade to more recent versions.

Copyright and License

Copyright (c) 2015-2020, Daniel Doubrovkine, Artsy and Contributors.

This project is licensed under the MIT License.

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The easiest way to write a Slack bot in Ruby.

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