Her

Her is an ORM (Object Relational Mapper) that maps REST resources to Ruby objects. It is designed to build applications that are powered by a RESTful API instead of a database.

Installation

In your Gemfile, add:

gem "her"

That’s it!

Upgrade

Please see the UPGRADE.md file for backward compability issues.

Usage

First, you have to define which API your models will be bound to. For example, with Rails, you would create a new config/initializers/her.rb file with these lines:

# config/initializers/her.rb
Her::API.setup :url => "https://api.example.com" do |connection|
  connection.use Faraday::Request::UrlEncoded
  connection.use Her::Middleware::DefaultParseJSON
  connection.use Faraday::Adapter::NetHttp
end

And then to add the ORM behavior to a class, you just have to include Her::Model in it:

class User
  include Her::Model
end

After that, using Her is very similar to many ActiveModel-like ORMs:

User.all
# GET https://api.example.com/users and return an array of User objects

User.find(1)
# GET https://api.example.com/users/1 and return a User object

@user = User.create(:fullname => "Tobias Fünke")
# POST "https://api.example.com/users" with the data and return a User object

@user = User.new(:fullname => "Tobias Fünke")
@user.occupation = "actor"
@user.save
# POST https://api.example.com/users with the data and return a User object

@user = User.find(1)
@user.fullname = "Lindsay Fünke"
@user.save
# PUT https://api.example.com/users/1 with the data and return+update the User object

You can look into the examples directory for sample applications using Her.

Middleware

Since Her relies on Faraday to send HTTP requests, you can choose the middleware used to handle requests and responses. Using the block in the setup call, you have access to Faraday’s connection object and are able to customize the middleware stack used on each request and response.

Authentication

Her doesn’t support authentication by default. However, it’s easy to implement one with request middleware. Using the connection block, we can add it to the middleware stack.

For example, to add a API token header to your requests, you would do something like this:

class TokenAuthentication < Faraday::Middleware
  def initialize(app, options={})
    @app = app
    @options = options
  end

  def call(env)
    env[:request_headers]["X-API-Token"] = @options[:token] if @options.include?(:token)
    @app.call(env)
  end
end

Her::API.setup :url => "https://api.example.com" do |connection|
  # This token could be stored in the client session
  connection.use TokenAuthentication, :token => "bb2b2dd75413d32c1ac421d39e95b978d1819ff611f68fc2fdd5c8b9c7331192"

  connection.use Faraday::Request::UrlEncoded
  connection.use Her::Middleware::DefaultParseJSON
  connection.use Faraday::Adapter::NetHttp
end

Now, each HTTP request made by Her will have the X-API-Token header.

Parsing JSON data

By default, Her handles JSON data. It expects the resource/collection data to be returned at the first level.

// The response of GET /users/1
{ "id" : 1, "name" : "Tobias Fünke" }

// The response of GET /users
[{ "id" : 1, "name" : "Tobias Fünke" }]

However, you can define your own parsing method using a response middleware. The middleware should set env[:body] to a hash with three keys: data, errors and metadata. The following code uses a custom middleware to parse the JSON data:

# Expects responses like:
#
#     {
#       "result": {
#         "id": 1,
#         "name": "Tobias Fünke"
#       },
#       "errors" => []
#     }
#
class MyCustomParser < Faraday::Response::Middleware
  def on_complete(env)
    json = MultiJson.load(env[:body], :symbolize_keys => true)
    env[:body] = {
      :data => json[:result],
      :errors => json[:errors],
      :metadata => json[:metadata]
    }
  end
end

Her::API.setup :url => "https://api.example.com" do |connection|
  connection.use Faraday::Request::UrlEncoded
  connection.use MyCustomParser
  connection.use Faraday::Adapter::NetHttp
end

OAuth

Using the faraday_middleware and simple_oauth gems, it’s fairly easy to use OAuth authentication with Her.

In your Gemfile:

gem "her"
gem "faraday_middleware"
gem "simple_oauth"

In your Ruby code:

# Create an application on `https://dev.twitter.com/apps` to set these values
TWITTER_CREDENTIALS = {
  :consumer_key => "",
  :consumer_secret => "",
  :token => "",
  :token_secret => ""
}

Her::API.setup :url => "https://api.twitter.com/1/" do |connection|
  connection.use FaradayMiddleware::OAuth, TWITTER_CREDENTIALS
  connection.use Faraday::Request::UrlEncoded
  connection.use Her::Middleware::DefaultParseJSON
  connection.use Faraday::Adapter::NetHttp
end

class Tweet
  include Her::Model
end

@tweets = Tweet.get("/statuses/home_timeline.json")

Caching

Again, using the faraday_middleware makes it very easy to cache requests and responses:

In your Gemfile:

gem "her"
gem "faraday_middleware"

In your Ruby code:

class MyCache < Hash
  def read(key)
    if cached = self[key]
      Marshal.load(cached)
    end
  end

  def write(key, data)
    self[key] = Marshal.dump(data)
  end

  def fetch(key)
    read(key) || yield.tap { |data| write(key, data) }
  end
end

# A cache system must respond to `#write`, `#read` and `#fetch`.
# We should be probably using something like Memcached here, not a global object
$cache = MyCache.new

Her::API.setup :url => "https://api.example.com" do |connection|
  connection.use Faraday::Request::UrlEncoded
  connection.use FaradayMiddleware::Caching, $cache
  connection.use Her::Middleware::DefaultParseJSON
  connection.use Faraday::Adapter::NetHttp
end

class User
  include Her::Model
end

@user = User.find(1)
# GET /users/1

@user = User.find(1)
# This request will be fetched from the cache

Relationships

You can define has_many, has_one and belongs_to relationships in your models. The relationship data is handled in two different ways.

If Her finds relationship data when parsing a resource, that data will be used to create the associated model objects on the resource.
If no relationship data was included when parsing a resource, calling a method with the same name as the relationship will fetch the data (providing there’s an HTTP request available for it in the API).

For example:

class User
  include Her::Model
  has_many :comments
  has_one :role
  belongs_to :organization
end

class Comment
  include Her::Model
end

class Role
  include Her::Model
end

class Organization
  include Her::Model
end

If there’s relationship data in the resource, no extra HTTP request is made when calling the #comments method and an array of resources is returned:

@user = User.find(1) 
# { 
#   :data => {
#     :id => 1,
#     :name => "George Michael Bluth",
#     :comments => [
#       { :id => 1, :text => "Foo" },
#       { :id => 2, :text => "Bar" }
#     ],
#     :role => { :id => 1, :name => "Admin" },
#     :organization => { :id => 2, :name => "Bluth Company" }
#   }
# }
@user.comments
# [#<Comment id=1 text="Foo">, #<Comment id=2 text="Bar">]
@user.role
# #<Role id=1 name="Admin">
@user.organization
# #<Organization id=2 name="Bluth Company">

If there’s no relationship data in the resource, Her makes a HTTP request to retrieve the data.

@user = User.find(1)
# { :data => { :id => 1, :name => "George Michael Bluth", :organization_id => 2 }}

# has_many relationship:
@user.comments
# GET /users/1/comments
# [#<Comment id=1>, #<Comment id=2>]

# has_one relationship:
@user.role
# GET /users/1/role
# #<Role id=1>

# belongs_to relationship:
@user.organization
# (the organization id comes from :organization_id, by default)
# GET /organizations/2
# #<Organization id=2>

Subsequent calls to #comments, #role and #organization will not trigger extra HTTP requests and will return the cached objects.

Hooks

You can add before and after hooks to your models that are triggered on specific actions (save, update, create, destroy):

class User
  include Her::Model
  before_save :set_internal_id

  def set_internal_id
    self.internal_id = 42 # Will be passed in the HTTP request
  end
end

@user = User.create(:fullname => "Tobias Fünke")
# POST /users&fullname=Tobias+Fünke&internal_id=42

Custom requests

You can easily define custom requests for your models using custom_get, custom_post, etc.

class User
  include Her::Model
  custom_get :popular, :unpopular
  custom_post :from_default
end

User.popular
# GET /users/popular
# [#<User id=1>, #<User id=2>]

User.unpopular
# GET /users/unpopular
# [#<User id=3>, #<User id=4>]

User.from_default(:name => "Maeby Fünke")
# POST /users/from_default?name=Maeby+Fünke
# #<User id=5 name="Maeby Fünke">

You can also use get, post, put or delete (which maps the returned data to either a collection or a resource).

class User
  include Her::Model
end

User.get(:popular)
# GET /users/popular
# [#<User id=1>, #<User id=2>]

User.get(:single_best)
# GET /users/single_best
# #<User id=1>

Also, get_collection (which maps the returned data to a collection of resources), get_resource (which maps the returned data to a single resource) or get_raw (which yields the parsed data return from the HTTP request) can also be used. Other HTTP methods are supported (post_raw, put_resource, etc.).

class User
  include Her::Model

  def self.popular
    get_collection(:popular)
  end

  def self.total
    get_raw(:stats) do |parsed_data|
      parsed_data[:data][:total_users]
    end
  end
end

User.popular
# GET /users/popular
# [#<User id=1>, #<User id=2>]
User.total
# GET /users/stats
# => 42

You can also use full request paths (with strings instead of symbols).

class User
  include Her::Model
end

User.get("/users/popular")
# GET /users/popular
# [#<User id=1>, #<User id=2>]

Custom paths

You can define custom HTTP paths for your models:

class User
  include Her::Model
  collection_path "/hello_users/:id"
end

@user = User.find(1)
# GET /hello_users/1

You can also include custom variables in your paths:

class User
  include Her::Model
  collection_path "/organizations/:organization_id/users"
end

@user = User.find(1, :_organization_id => 2)
# GET /organizations/2/users/1

@user = User.all(:_organization_id => 2)
# GET /organizations/2/users

@user = User.new(:fullname => "Tobias Fünke", :organization_id => 2)
@user.save
# POST /organizations/2/users

Multiple APIs

It is possible to use different APIs for different models. Instead of calling Her::API.setup, you can create instances of Her::API:

# config/initializers/her.rb
$my_api = Her::API.new
$my_api.setup :url => "https://my_api.example.com" do |connection|
  connection.use Faraday::Request::UrlEncoded
  connection.use Her::Middleware::DefaultParseJSON
  connection.use Faraday::Adapter::NetHttp
end

$other_api = Her::API.new
$other_api.setup :url => "https://other_api.example.com" do |connection|
  connection.use Faraday::Request::UrlEncoded
  connection.use Her::Middleware::DefaultParseJSON
  connection.use Faraday::Adapter::NetHttp
end

You can then define which API a model will use:

class User
  include Her::Model
  uses_api $my_api
end

class Category
  include Her::Model
  uses_api $other_api
end

User.all
# GET https://my_api.example.com/users

Category.all
# GET https://other_api.example.com/categories

SSL

When initializing Her::API, you can pass any parameter supported by Faraday.new. So to use HTTPS, you can use Faraday’s :ssl option.

ssl_options = { :ca_path => "/usr/lib/ssl/certs" }
Her::API.setup :url => "https://api.example.com", :ssl => ssl_options do |connection|
  connection.use Faraday::Request::UrlEncoded
  connection.use Her::Middleware::DefaultParseJSON
  connection.use Faraday::Adapter::NetHttp
end

Testing

Using Faraday stubbing feature, it’s very easy to write tests for our models. For example, using RSpec:

# app/models/post.rb
class Post
  include Her::Model
  custom_get :popular
end

# spec/models/post.rb
describe Post do
  before do
    Her::API.setup :url => "http://api.example.com" do |connection|
      connection.use Her::Middleware::FirstLevelParseJSON
      connection.use Faraday::Request::UrlEncoded
      connection.adapter :test do |stub|
        stub.get("/users/popular") { |env| [200, {}, [{ :id => 1, :name => "Tobias Fünke" }, { :id => 2, :name => "Lindsay Fünke" }].to_json] }
      end
    end
  end

  describe ".popular" do
    it "should fetch all popular posts" do
      @posts = Post.popular
      @posts.length.should == 2
    end
  end
end

Things to be done

Better error handling
Better API documentation (using YARD)

Contribute

Yes please! Feel free to contribute and submit issues/pull requests on GitHub.

How to contribute

Fork the repository
Implement your feature or fix
Add examples that describe it (in the spec directory)
Make sure bundle exec rake spec passes after your modifications
Commit (bonus points for doing it in a feature-* branch)
Send a pull request!

Contributors

These fine folks helped with Her:

jmlacroix / her

Her