api_client_inhertiance_example.rb

# Wrapper around a HTTP library
class ApiClient; ... end

# Knows how to decode JSON responses from the API
class JSONApiClient < ApiClient; ... end

# Knows how to decode XML responses from the API
class XMLApiClient < ApiClient; ... end

# Exposes an API's endpoints as methods on an object
class MyAppApiClient
  attr_reader :json_client
  attr_reader :xml_client

  def initialize(api_token)
    @json_client = JSONApiClient.new(api_token)
    @xml_client = XMLApiClient.new(api_token)
  end

  def current_account
    json_client.get('/api/current_account')
  end

  def balance
    xml_client.get('/api/current_account/balance')
  end
end