Ruby DSL block stylesEdit

Created 2/22/2010, updated 5/18/2017

This article provides an excellent overview of the two main DSL "block styles" available in Ruby:

Either, redefining self and using instance_eval:

adapter.config do
  height 700
  width 500
end

Or, passing in a "configurator" object:

adapter config do |c|
  c.height 700
  c.width 500
end

The advantage of the former is the clean syntax, but the disadvantage is that by changing self you might break message sends that rely on an implicit (and different) self value; eg:

def width_helper
  # complicated calculation...
end

adapter.config do
  height 700
  width width_helper # NoMethodError raised here
end

A third style not mentioned in the article is to use subclasses:

class MyConfig < Config
  def config
    height 700 # height method defined in Config superclass
    width 500 # width method defined in Config superclass
  end
end