Interfacing with a third-party API in Rails? ( Opening URLs and Parsing XML/JSON )

Question

I'm working on a Rails project which will need to interface with multiple third-party APIs. I'm pretty new to Rails, and I've never done this before, so I'm lacking some basic information here. Specifically, What is the preferred Rails way of simply querying an external URL?

In the PHP world, it was cURL. You take whatever the resource URL is, throw cURL at it, and start processing the response, whether it be XML, JSON, etc.

So, what's the cURL equivalent in Rails? While we're at it, what is the preferred method of parsing XML and JSON responses? My instincts are to Google around for some Ruby gems to get the job done, but this is such a practical problem that I wouldn't be surprised if the Rails community had already worked out a tried-and-true solution to this kind of problem.

If it's of any contextual value, I plan to run these third-party API interactions as nightly cronjobs, probably all packaged up as custom rake tasks.

Thanks for sharing your expertise.

Answer 1

for opening urls you can use open-uri

just

require 'open-uri'
file_handle = open("http://google.com/blah.xml")

to parse xml you can use Nokogiri

$ gem install nokogiri

document = Nokogiri::XML(file_handle)
document/"xpath/search"

very powerful library, can do all kinds of searching and modifying for both XML and HTML

same for html Nokogiri::HTML

there is also lots of JSOM support out there too

checkout Nokogiri also Hpricot is good for XML/HTML

for JSON in rails

parsed_json = ActiveSupport::JSON.decode(your_json_string)

parsed_json["results"].each do |longUrl, convertedUrl|
  site = Site.find_by_long_url(longUrl)
  site.short_url = convertedUrl["shortUrl"]
  site.save
end

see this question: How do I parse JSON with Ruby on Rails?

Answer 2

In a perfect world, a gem already exists for the API you want to use, and you would just use that. Otherwise, you have a few options:

• ActiveResource might make sense for you depending on the complexity of the API you want to use. For example, here's an old (and no longer functional) example of using ActiveResource to connect to the Twitter API
• Net::Http is lower-level, but certainly does the trick
• open-uri is a wrapper for net/http
• Curb uses libcurl to get things done

Parsing JSON is generally very straightforward. For XML, as stated in another answer, Nokogiri is probably the way to go.