A super-easy and great way to implement Gem configuration

[gsw]

Just did this in my constance gem, and totally love it as a way to add configuration or options configurability to your gem:
http://stufftohelpyouout.blogspot.com/2012/09/forget-struct-and-openstruct-flexible.html

like:

module MyModule
  class << self
    attr_accessor :debug, :proc, :some_mapping
    def configure(&block); yield; end
  end
end

I've seen people that use OpenStruct, Struct, and I had my own way to do it before this, but this seems a lot better.

[gsw]

On Sunday, September 23, 2012 8:11:43 AM UTC-4, Ilia Bylich wrote:

I am not sure that this way is simple. I usually use for gem configuration this code

require 'active_support/configurable'

module GemModule

  include ActiveSupport::Configurable

  class << self

    def setup

      yield config

    end

  end

end

And then you can write

GemModule.setup do |config|

  config.option1 = "value1"

  config.option2 = 2

end

And

GemModule.config.option1

# => "value1"

Moreover, you can define method_missing in you module and delegate unknown methods to self.config. Then you will be able to write

GemModule.option1

# => "value1"

http://api.rubyonrails.org/classes/ActiveSupport/Configurable.html

That works, but it has the following disadvantages over the method I described:

1. If you use ActiveSupport::Configurable you are tied to using activesupport/Rails. Many times you want to write the Gem so that it isn't Rails-specific and want to limit dependencies.
2. I know Rails uses the "pass the config into the block thing", but it isn't as DRY as not typing "config." before each parameter.
3. By defining the attr_accessors, you limit the chance that a user will mistype/misspell a variable.
4. The way you described allows the user to define config parameters with procs and lambdas, but the way I describe allows the user to define "config parameters" as procs, lambdas, and methods, i.e. the user can actually just define a variable as:

def some_variable_name
  # some really involved implementation here, even refactored into various methods, etc. in the block.
end

See more at: http://stufftohelpyouout.blogspot.com/2012/09/forget-struct-and-openstruct-flexible.html

Hope that helps.

[gsw]

Just as an update, I had bugs in the previous code provided and fixed with help from Jesús Gabriel y Galán and Calvin B. on the list in this post: http://www.ruby-forum.com/topic/4406183

module MyModule
  class << self
    attr_accessor :debug, :proc_or_lambda, :some_array, :some_hash, :time 
    def configure(&blk); class_eval(&blk); end
  end
end

and can configure like:

MyModule.debug = true

MyModule.proc_or_lambda = lambda{|a,b| puts "a=#{a} b=#{b}"}

# ...

or

MyModule.configure do
  @debug = true
  @proc_or_lambda = lambda{|a,b| puts "a=#{a} b=#{b}"}
  @some_array = [:foo,:bar]
  @some_mapping = {:key => 'value'}
  def self.time; Time.now; end
end

or

MyModule.configure do
  self.debug = true
  self.proc_or_lambda = lambda{|a,b| puts "a=#{a} b=#{b}"}
  self.some_array = [:foo,:bar]
  self.some_mapping = {:key => 'value'}
  def self.time; Time.now; end
end

Posted here with more examples:
http://stufftohelpyouout.blogspot.com/2012/09/forget-struct-and-openstruct-flexible.html