ApiProvider refactoring - http://blog.arkency.com/2013/05/is-it-cute-or-ugly

api_client.rb

require 'delegate'
require 'faraday'

class ApiClient < SimpleDelegator
  def initialize(args = {})
    args = defaults.merge(args)
    
    @login = args.fetch(:login)
    @password = args.fetch(:password)
    
    super(connection) # api_client.get("/foo") will be delegated to connection
  end
  
  # you could make connection private,
  # but I can see a number of situations where you will want to access it directly
  #
  # you could define this in the initializer as an args.fetch(:connection) default,
  # but experience tells me that you will want VCR or Faraday stubs,
  # mocks don't work well in this situation
  def connection
    #                            v https is a must !!!
    @connection ||= Faraday.new("https://api.example.org/query", api_credentials)
    #                                                            ^ every request will include the api_credentials
  end
  
  private
  
    attr_reader :username, :password
  
    def api_credentials
      {
        :usr => login,
        :pwd => password 
      }
    end
  
    def defaults
      {
        :login    => ENV['APIPROVIDER_LOGIN'],
        :password => ENV['APIPROVIDER_PASSWORD'],
      }
    end
end

original.rb

class ApiProvider
  def initialize(login = nil, password = nil)
    login    ||= ENV['APIPROVIDER_LOGIN']
    password ||= ENV['APIPROVIDER_PASSWORD']
    @uri       = Addressable::URI.parse("http://api.example.org/query")
    @uri.query_values = {usr: login, pwd: password}
  end
end

refactored.rb

class ApiProvider
  def initialize(args = {})
    args = defaults.merge(args)
    
    @login = args.fetch(:login)
    @password = args.fetch(:password)
  end
  
  private
  
    attr_reader :username, :password
    
    def defaults
      {
        :login    => ENV['APIPROVIDER_LOGIN'],
        :password => ENV['APIPROVIDER_PASSWORD'],
      }
    end
end

The constructor should know about defaults, that's its job.

Structs are under-used in my opinion. I've released HStruct recently, it helps me a lot with simple data structures. Some benchmarks were surprising.

As for the @uri, it doesn't belong in the initialize. api_client.rb is what I'm thinking.