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Slack Poster

slack-poster is a simple gem to make your integration with Slack easier. It supports only incoming communications (from you to Slack).


Add this line to your application's Gemfile:

$ gem 'slack-poster'

And then execute:

$ bundle

Or install it yourself as:

$ gem install slack-poster

Slack setup

This gem will use a Incoming WebHook integration on Slack. First, you need to create a new Incoming Webhook integration at (where "team-name" should be your own team name).

Hit "Add Incoming WebHooks Integration" and go to the next screen. Here you can add a name to your integration, customize the username that will post and the icon.

Copy the Webhook URL, because you'll need it. Click "Save Settings" and you're done.


First you have to initialize your poster and then you can use send_message to send your message.

poster =
poster.send_message('Hello world!')

You can use an options array if you don't want to use the default settings:

options = {
  icon_url: '',
  # or icon_emoji: 'emoji_name',
  username: 'Tester',
  channel: '#random'

And then use it as a second parameter. Note that every option is optional (no pun intended!).

poster =, options)
poster.send_message('Hello with options')
# posts message 'Hello with options' to #random with the username 'Tester'

Or you can change the options whenever you want

poster =
poster.username = 'TestUser'
poster.icon_emoji = ':ghost:'
poster.send_message('Hello World') # => "ok"
# posts message 'Hello World' to #random with the username 'TestUser' and ghost emoji as avatar

You can also send a Slack::Message object instead of String:

message ='hello slack')

Message attachments

Slack Poster supports message attachments. To do so you have to create Slack::Attachment objects and then attach them to a Slack::Message object. Read the official documentation to understand how attachments work and see different examples of attachments in practice.

You can build a basic attachment and them attach it to a message and use a poster to post that message for you:

# As an alternative you could also initialize the attachment with all the fields
# 'fallback', pretext: 'pretext', ....)
attachment =

# This text will be used in clients that don't show formatted text (eg. IRC, mobile notifications)
attachment.fallback = "You wouldn't believe who's a mighty pirate!"

attachment.pretext = 'Arrrgh'
attachment.color = 'danger' # good, warning, danger, or any hex color code (eg. #439FE0)

attachment.image_url = ''
# you can use thumb_url instead for a small thumb pulled to the right

attachment.text = 'To become a mighty pirate Guybrush had to go through the three trials.'
attachment.title = 'Mighty pirate'
attachment.title_link = ''

# If you want to include author information you can use the following methods:
# attachment.author_name
# attachment.author_icon
# attachment.author_link
# Check Slack documentation for more info.

message ='Monkey island news', attachment)

# You can also add the attachment after initializing the message:
# message ='Monkey island news')
# message.attachments << attachment

poster =
poster.username = 'Monkey Island Daily'
poster.icon_emoji = ':monkey_face:'
poster.send_message(message) # => "ok"

This will create a message like this one:


Slack attachment can contain fields that will be displayed in a table inside the message attachment. You can add fields with Slack::Attachment#add_field:

attachment =
attachment.add_field('Name1', 'Value1')
attachment.add_field('Name2', 'Value2')
attachment.add_field('Name3', 'Value3')
attachment.add_field('Name4', 'Value4')

message ='What a beautiful table of names and values', attachment)

poster =
poster.send_message(message) # => "ok"

You may notice that the message will display with a vertical list of fields. You can have them side by side giving a third boolean parameter (is it a short field?).

attachment =
attachment.add_field('Name1', 'Value1', true)
attachment.add_field('Name2', 'Value2', true)
attachment.add_field('Name3', 'Value3')
attachment.add_field('Name4', 'Value4')

This way the first two field will be displayed in the same row.


  1. Fork it ( )
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Add some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create new Pull Request