ruby-ess

Generate and parse ESS XML feeds with Ruby

Installation

Add this line to your application's Gemfile:

gem 'ess', '~> 1.0.0'

And then execute:

$ bundle

Or install it yourself as:

$ gem install ess -v 1.0.0

Information

RDoc documentation available on RubyDoc.info
Source code available on GitHub

Usage

Producing your own ESS feeds is easy. Here is a rather extensive example about how it's done, with most of the available tags available in ESS:

require 'ess'

ess = ESS::Maker.make do |ess|
  ess.channel do |channel|
    channel.title "National Stadium Football events"
    channel.link "http://sample.com/feeds/sample.ess"
    channel.id "ESSID:50b4b412-1ad4-a731-1c6a-2523ffa33f81"
    channel.published "2012-12-13T08:29:29Z"
    channel.updated "2012-12-13T18:30:02-08:00"
    channel.rights "Copyright (c) 2013, John Doe"

    channel.add_feed do |feed|
      feed.title "Football match of saturday"
      feed.uri "http://sample.com/events/specific-and-unique-event-page/"
      feed.id "EVENTID:550b55b412-1ad4-a4731-155-2777fa37f866"
      feed.published "2012-12-13T08:29:29Z"
      feed.updated "2012-12-13T18:30:02-0800"
      feed.access "PUBLIC"
      feed.description("Welcome to my first football match event. " +
                       "This football match is very important. " +
                       "Our team is about to go up against our main league competitor.")

      feed.tags do |tags|
        tags.tag "Sport"
        tags.tag "Footbal"
        tags.tag "Soccer"
        tags.tag "Match"
        tags.tag "Game"
        tags.tag "Team Sport"
        tags.tag "Stadium"
      end

      feed.categories.add_item(:type => "competition") do |item|
        item.name "Football"
        item.id "C2AH"
      end

      feed.dates.add_item do |item|
        item.type_attr "recurrent"
        item.unit_attr "week"
        item.limit_attr "4"
        item.selected_day_attr "saturday,sunday"

        item.name "Match Date"
        item.start "2011-12-13T18:30:02Z"
        item.duration "10800"
      end

      feed.places do |places|
        places.add_item(:type => "fixed", :priority => 1) do |item|
          item.name "Football Stade"
          item.latitude "40.71675"
          item.longitude "-74.00674"
          item.address "Ave of Americas, 871"
          item.city "New York"
          item.zip "10001"
          item.state_code "NY"
          item.country_code "US"
        end

        places.add_item(:type => "fixed", :priority => 2) do |item|
          item.name "Match direct on TV"
          item.country_code "US"
          item.medium_name "NBC super channel"
          item.medium_type "television"
        end
      end

      feed.prices do |prices|
        prices.add_item(:type => "standalone", :priority => 2) do |item|
          item.mode_attr "invitation"

          item.name "Free entrance"
          item.value "0"
          item.currency "USD"
        end

        prices.add_item(:type => "recurrent", :priority => 1) do |item|
          item.unit_attr "month"
          item.mode_attr "fixed"
          item.limit_attr "12"

          item.name "Subscribe monthly !"
          item.value "17"
          item.currency "USD"
          item.start "2012-12-13T18:30:02Z"
        end
      end

      feed.media do |media|
        media.add_item(:type => "image", :priority => 1) do |item|
          item.name "Stade image"
          item.uri "http://sample.com/small/image_1.png"
        end

        media.add_item(:type => "video", :priority => 3) do |item|
          item.name "Stade video"
          item.uri "http://sample.com/video/movie.mp4"
        end

        media.add_item(:type => "sound", :priority => 2) do |item|
          item.name "Radio spot"
          item.uri "http://sample.com/video/movie.mp3"
        end

        media.add_item(:type => "website", :priority => 4) do |item|
          item.name "Football Stade website"
          item.uri "http://my-football-website.com"
        end
      end

      feed.people do |people|
        people.add_item(:type => "organizer") do |item|
          item.id "THJP167:8URYRT24:BUEREBK:567TYEFGU:IPAAF"
          item.uri "http://michaeldoe.com"
          item.name "Michael Doe"
          item.firstname "Michael"
          item.lastname "Doe"
          item.organization "Football club association"
          item.address "80, 5th avenue / 45st E - #504"
          item.city "New York"
          item.zip "10001"
          item.state "New York"
          item.state_code "NY"
          item.country "United States of America"
          item.country_code "US"
          item.logo "http://sample.com/logo_120x60.png"
          item.icon "http://sample.com/icon_64x64.png"
          item.email "contact@sample.com"
          item.phone "+001 (646) 234-5566"
        end

        people.add_item(:type => "performer") do |item|
          item.id "FDH56:G497D6:4564DD465:4F6S4S6"
          item.uri "http://janettedoe.com"
          item.name "Janette Doe"
        end

        people.add_item(:type => "attendee") do |item|
          item.name "Attendees information:"
          item.minpeople 0
          item.maxpeople 500
          item.minage 0
          item.restriction "Smoking is not allowed in the stadium"
        end

        people.add_item(:type => "social") do |item|
          item.name "Social network link to share or rate the event."
          item.uri "http://social_network.com/my_events/my_friends/my_notes"
        end

        people.add_item(:type => "author") do |item|
          item.name "Feed Powered by Event Promotion Tool"
          item.uri "http://sample.com/my_events/"
          item.logo "http://sample.com/logo_120x60.png"
          item.icon "http://sample.com/icon_64x64.png"
        end

        people.add_item(:type => "contributor") do |item|
          item.name "Jane Doe"
        end
      end

      feed.relations do |relations|
        relations.add_item(:type => "alternative") do |item|
          item.name "alternative event"
          item.id "EVENTID:50412:1a904:a715731:1cera:25va33"
          item.uri "http://sample.com/feed/event_2.ess"
        end

        relations.add_item(:type => "related") do |item|
          item.name "related event title"
          item.id "EVENTID:50b412:1a35d4:a731:1354c6a:225dg1"
          item.uri "http://sample.com/feed/event_3.ess"
        end

        relations.add_item(:type => "enclosure") do |item|
          item.name "nearby event"
          item.id "EVENTID:50b12:3451d4:34f5a71:1cf6a:2ff81"
          item.uri "http://sample.com/feed/event_5.ess"
        end
      end
    end
  end
end

As can be seen, it's a very Builder-like DSL. The result of this code will be an ESS feed with one item. To get XML from it, the 'to_xml!' method ca be used.

More information on ESS and what tags and options are available can be found on http://essfeed.org/ .

Pushing feeds to aggregators

Once a feed is generated, it can be submitted to an aggregator easily. To send it to the default aggregator service, which is Robby, just add an option to the 'make' class method:

ess = ESS::Maker.make(:push => true) do |ess|

  ...

end

Another way to do the same is to first generate the feed and assign the result to a variable, like 'ess' in previous example, and call its 'push_to_aggregators' method. It accepts the same options and is useful for example when the feed has to be submitted in a dalayed job.

In a Rails environment, if the feed is generated in response to a request, providing the request object to the maker method could provide the aggregator with more useful data:

ess = ESS::Maker.make(:request => request) do |ess|

  ...

end

Should you want to provide a list of aggregator services yourself, it can be done with the aggregators option:

ess = ESS::Maker.make(:aggregators => ['http://aggregator.example.com/api.json', ...]) do |ess|

  ...

end

Another option is to set a new default list of aggregator services using the ESS::Pusher class:

ESS::Pusher.aggregators = ['http://aggregator.example.com/api.json', ...]

Validation

When using the ESS::Maker class, the resulting feed is validated automatically at the end of the block. That means that before the block ends, the feed has to have all the mandatory tags, with valid values. There is however an option to turn that behavior off, but there should be a good reason to do that.

ess = ESS::Maker.make(:validate => false) do |ess|

  ...

end

The resulting object accepts the 'valid?' and 'validate' methods. The former returns true or false, while the later raises an exception with a message more useful for debugging.

Working with tags

A tag with text can be specified like this:

ess = ESS::Maker.make do |ess|
  ess.channel do |channel|

    channel.title "National Stadium Football events"

    ...

  end
end

Each tag accepts method calls coresponding to child tag names. These methods can accept a string argument, which will become the text of the child tag, and/or a list of key/value pairs (options), which will become tag attributes.

If there is also a block, it should expect one parameter which will be a reference to the child tag.

For the case where a single tag can have multiple child tags with the same name, the following construct can be used:

ess = ESS::Maker.make do |ess|
  ess.channel do |channel|

    channel.add_feed do |feed|

      ...

    end

    channel.add_feed do |another_feed|

      ...

    end

    end
  end
end

For every tag 'tag_name' its parent accepts an 'add_tag_name' method, which accepts the same arguments as a 'tag_name' method.

Attributes have also their own methods for setting them, for example:

ess = ESS::Maker.make do |ess|
  ess.lang_attr "zu"

  ...

end

Here the 'lang' attribute of the ess tag is set to "zu". And there is also a 'text!' method, which can be used to set a tags text:

ess = ESS::Maker.make do |ess|
  ess.channel do |channel|

    channel.title do |title|
      title.text! "National Stadium Football events"
    end

    ...

  end
end

Again, more information on ESS and what tags and options are available can be found on http://essfeed.org/ .

Valid tag and attribute values

Pretty much anything can be used as the value for a tag, as long as it can be converted to a string with #to_s.

Tags that accept date or time will accept Time objects too, which will be converted to the corrent format, which is ISO-8601 for ESS. However, if the value is a string, an attempt will be made to automatically convert the value to the ISO-8601 format.

IDs

The channel and feed ID tags can also be computed automatically, they don't need to be set by hand. They are automatically calculated and set the first time the TITLE or URI/LINK tags are changed. Also, instead of using a valid ID value, any string can be assigned to the ID tag of a channel or feed, and if it doesn't start with "ESSID:" or "EVENTID:", it will be regenerated using that string as the key.

Parsing ESS files

There is also an ESS::Parser class, which has one method "#parse" which accepts a string containing the ESS/XML document, or a File object. It parses the document and returns an ESS::ESS object, which represents the root elements of an ESS document.

This object has methods which correspond to child tags, and each method retrieves another object which represents a child tag with that name, and which again has methods corresponding to its child elements. I believe it's all easier to understand from an example:

ess = ESS::Parser.parse(xml_doc)

# To retrieve a child tag, just use a method with the same name
title_tag = ess.channel.title

# To retrieve a tags text, use the #text! method
title_text = title_tag.text!

# Some tags car be repeated more then once. For that case the tag
# objects accept tag_name_list methods, which return a list of child
# tags named "tag_name", like this:
feeds = ess.channel.feed_list
feeds.each do |feed|
  puts feed.title.text!
end

# For reading attribute values, the objects accept attr_name_attr
# methods, for example, to retrieve the value of attribute "type" of
# a "item" tag:
item = feeds[0].dates.item_list[0]
date_item_type = item.type_attr

find_coming and find_between

To aid web developers who want to display events in a list or a calendar, the ESS::ESS objects returned by the parser have two additional methods: find_coming and find_between.

find_coming tries to find the next N events for your event list. It returns a list of hashes, each hash representing one item for the list. The hash contains the :time and :feed keys, the former being the start time of the event, and the later the complete feed describing the whole event.

find_coming accepts two parameters. The first parameter is the number of events it should return and the default is 10. The second parameter defaults to Time.now, and the method with return N events starting from the moment specified.

find_between returns a list of all events between the two moments in time, which as specified as parameters with Time objects. For example, to retrieve all events in June 2013, run this:

start_time = "2013-06-01 00:00"
end_time = "2013-06-30 24:00"
events = ess.find_between(start_time, end_time)

Contributing

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

License

(The MIT License)

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

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