Using rails to consume web services/apis

Question

I'm new to the rails world and am trying to build a app to simply allow me to search things on Amazon and such sites based on the users input.

I've done a little reasearch and it seems the httparty gem is a good place to start? The documents ive found so far though are not the best. They don't really give me a lot of information (where to put the code etc).

Are there any existing tutorials out there or code examples that I can either use or take a look at to give me a better idea of how this thing works?

Answer 1

I'm working on an app like this right now, so let me offer a few thoughts.

First, if you're a complete newcomer to Rails, then as a first step I'd suggest taking a parallel approach to the problem, with two tracks:

1. Learn about Rails
2. Learn about how to interact with an API (make requests and parse responses) in Ruby

These are two separate problems, and although you may end up implementing them together, it's best to think about them in isolation first.

For the first one, I'd suggest writing a couple simple apps first to get a feel for how things work. Even only a simple app will require a certain amount of user interaction, possibly saving records to the DB, etc., problems that are separate from consuming data from an API. There are an endless number of tutorials out there on Rails, but just to mention one, you might try Michael Harti's Learn Web Development with Rails as a starting point.

The second point, consuming API data, is distinct from the problems of designing the app itself. To learn more about this aspect of the problem, I'd suggest using a popular API client gem like (as you mentioned) HTTParty, which I use myself. Rather than immediately try to use the HTTParty methods in a Rails app, as an exercise I'd suggest playing around a bit in a console (irb). If you install the gem (gem install httparty) you can then require it (require 'httparty') from the console and immediately make requests and parse responses from the APIs.

E.g.:

irb(main):001:0> require 'httparty'
=> true
irb(main):002:0> response = HTTParty.get('http://twitter.com/statuses/public_timeline.json')
=> ...

Once you've got a bit more familiar with Rails and with accessing an API in ruby, then you could move on to actually building the app itself. Depending on how complex your requests to the API(s) are going to be, you have a few options as to how to structure your API requests in your Rails app:

1. Make the requests part of the Rails app itself, directly from controller actions. This is really only okay if you are only going to support a very limited number of request types (e.g. simple search) on a limited number of services. Anything more complex and your controller will get fat, which is a no-no in MVC frameworks.
2. Create a separate ruby class (usually called an API wrapper) to group together methods for making requests and parsing responses from the API. With a gem like HTTParty you can do this just by adding a line include HTTParty in the class, which adds the module to the class. There are lots of examples out there on how to do this, here is one.
3. Use a dedicated gem for accessing specific APIs, or create one (or more) yourself. There are gems for most popular services, e.g. Twitter, Linkedin, Flickr, etc. See this list of API client gems for more. This takes away a lot of the pain of interacting with an API, but will only work for a subset of all services.

You mention you're thinking of using HTTParty, which I can recommend as I am using it myself. There are alternatives such as Faraday (see this list of HTTP clients for more), but I find for most tasks HTTParty will do fine. The documentation may be a bit sparse, but there are a bunch of examples that you can work from.

Hope that helps!