Generate and parse ESS XML feeds with Ruby
Add this line to your application's Gemfile:
gem 'ess', '~> 1.0.0'
And then execute:
Or install it yourself as:
$ gem install ess -v 1.0.0
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 "email@example.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', ...]
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.
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.dates.item_list 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)
- 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
(The MIT License)
Copyright (c) 2013 Robby
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