Allow my own class in Rails to be configured with block syntax - ruby-on-rails-3

Question

I often see code of the form
RSpec.configure do |config|
config.include ApiHelper
# ## Mock Framework
#
# If you prefer to use mocha, flexmock or RR, uncomment the appropriate line:
#
# config.mock_with :mocha
# config.mock_with :flexmock
# config.mock_with :rr
# Remove this line if you're not using ActiveRecord or ActiveRecord fixtures
config.fixture_path = "#{::Rails.root}/spec/fixtures"
# If you're not using ActiveRecord, or you'd prefer not to run each of your
# examples within a transaction, remove the following line or assign false
# instead of true.
config.use_transactional_fixtures = true
# If true, the base class of anonymous controllers will be inferred
# automatically. This will be the default behavior in future versions of
# rspec-rails.
config.infer_base_class_for_anonymous_controllers = false
config.include FactoryGirl::Syntax::Methods
end
Is there a feature in Rails that lets me do something similar? I want to be able to configure my own library with a similar syntax within config/initializers/my_class.rb
MyClass.configure do |config|
# allow configuration here
end

Answer 1

Nothing special is needed in Rails - it is simple Ruby code. Here is how it can be done:
class MyClass
def self.configure(&block)
a_hash = { :car => "Red" }
puts "Hello"
yield a_hash
puts "There"
end
end
MyClass.configure do |config|
puts "In Block"
puts config[:car]
end
Output:
Hello
In Block
Red
There
I am yielding a hash, but you can yield whatever object you want to.

Answer 2

Rails will load all the Ruby files in the config/initializers directory when starting up the server.
If you want to use the same style for your own custom configurable class then you just have to implement a configure class method that accepts a block and passes a configuration object to that block. e.g.
class MyClassConfiguration
# configuration attributes
end
class MyClass
def self.configure
yield configuration if block_given?
end
def self.configuration
#config ||= MyClassConfiguration.new
end
end
Using phoet's gem would be even easier.
Its worth taking a look at how RSpec does it if you are curious:
The RSpec.configure method is in https://github.com/rspec/rspec-core/blob/master/lib/rspec/core.rb
The Configuration class is implemented in https://github.com/rspec/rspec-core/blob/master/lib/rspec/core/configuration.rb

Answer 3

i don't know if rails provides a helper for that, but i wrote my own tiny solution for this problem that i use in several gems: https://github.com/phoet/confiture
it let's you define configurations:
module Your
class Configuration
include Confiture::Configuration
confiture_allowed_keys(:secret, :key)
confiture_defaults(secret: 'SECRET_STUFF', key: 'EVEN_MOAR_SECRET')
end
end
and have an easy api to do the configuration:
Your::Configuration.configure do |config|
config.secret = 'your-secret'
config.key = 'your-key'
end
besides this, there are a lot of other config tools out there like configatron or simpleconfig.

Answer 4

A global configuration set via the block.
module VkRobioAPI
module Configuration
OPTION_NAMES = [
:client_id,
:redirect_uri,
:display,
:response_type
]
attr_accessor *OPTION_NAMES
def configure
yield self if block_given?
self
end
end
end
module VkRobioAPI
extend VkRobioAPI::Configuration
class << self
def result
puts VkRobioAPI.client_id
end
end
end
Example:
VkRobioAPI.configure do |config|
config.client_id = '3427211'
config.redirect_uri = 'bEWLUZrNLxff1oQpEa6M'
config.response_type = 'http://localhost:3000/oauth/callback'
config.display = 'token'
end
Result:
VkRobioAPI.result
#3427211
#=> nil

Answer 5

If you are using rails, you can just include ActiveSupport::Configurable into your class and off you go. Outside of rails, you will have to add the activesuport gem to your Gemfile or gemspec and then call require 'active_support/configurable'.
Example
class MyClass
include ActiveSupport::Configurable
end
Usage
With block
MyClass.configure do |config|
config.key = "something"
config.key2 = "something else"
end
or inline, without block
MyClass.config.key = "something"
MyClass.config.key2 = "something else"
or like a hash
MyClass.config[:key] = "somehting"
MyClass.config[:key2] = "something else"
Note: key can be any character of your choice.