This post originated from an RSS feed registered with Ruby Buzz by Gabriel Horner. Original Post: Block to Hash Conversion for Ruby Config Blocks Feed Title: Tagaholic Feed URL: http://feeds2.feedburner.com/tagaholic Feed Description: My ruby/rails/knowledge management thoughts Latest Ruby Buzz Posts Latest Ruby Buzz Posts by Gabriel Horner Latest Posts From Tagaholic

While I was busy scratching an irb itch, I came up with a handy technique for converting a method’s block definition into a hash. Here’s an example of using such a method:

  Alias.init do |a|
    a.verbose = true
    a.constant = {'Array' = 'A'}
    a.instance_method = {'String'=>{'downcase'=>'dc' },'Array'=>{'select'=>'s'}}
  end

What I wanted was a quick but clean way to convert the data structure described in the method’s block to a hash. So knowing about OpenStruct, I peered into its internals and saw that it stores its attributes as a hash in @table. Since there isn't a public method for @table, I realized I was going to have to use instance_variable_get(:@table). Now if I only wanted to be quick, I could simply have used that. But wanting code clarity (ie not have to read OpenStruct’s internal variables each time) and to avoid monkeypatching (I have been bitten), I came up with:

Using it is simple. Pass your method’s block to ConfigStruct.block_to_hash() and you’ll get back a hash with whatever was defined in the block:

  def init(*args, &block)
    config = ConfigStruct.block_to_hash(block)
    #process your config ...
  end
     
  init do |c|
    c.some = "config"
    c.info = "goes here"
  end
  # In init(), config = {:some=>'config', :info=>'goes here'}

If you decide to not pass your method a block? No worries. You get back an empty hash. To see this idea in my ruby gem, see here.