Raise error if "initialize" method name is misspelled

initialize_spellcheck.rb

# Public: Implementation of "Strike a match" algorithm for calculating
# similarity between strings.
#
# http://www.catalysoft.com/articles/StrikeAMatch.html
#
# Examples
#
#   checker = StringSimilarityChecker.new('Quick brown fox')
#
#   checker =~ 'quick brown ox'                  #=> true
#   checker.similarity_index('quick brown ox')   #=> 0.947
#
#   checker =~ 'quick frown pox'                 #=> true
#   checker.similarity_index('quick frown pox')  #=> 0.8
#
#   checker =~ 'quick lawn ducks'                #=> false
#   checker.similarity_index('quick lawn ducks') #=> 0.476
class StringSimilarityChecker
  def initialize base_string, similarity_treshold = 0.8
    @base_pairs = character_pairs base_string
    @treshold   = similarity_treshold
  end

  # Public: Check if similarity index with given string passes the treshold.
  def similar_to? string
    similarity_index(string) >= @treshold
  end
  alias =~ similar_to?

  # Public: Calculate similarity index between given and base strings.
  #
  # Returns a Float between 0 and 1.
  def similarity_index string
    pairs  = character_pairs string
    shared = count_identical_pairs @base_pairs, pairs
    (2 * shared).to_f / (@base_pairs.size + pairs.size)
  end

  SPACE = ' '

  # Internal: Break string into pairs of adjacent characters, excluding ones
  # that contain spaces.
  def character_pairs str
    str = str.to_str.downcase
    (0..(str.size-2)).map {|pos| str[pos,2] }.reject {|pair| pair.include? SPACE }
  end

  # Internal: Measure the intersection between two arrays of character pairs.
  def count_identical_pairs pairs1, pairs2
    size, pairs2 = 0, pairs2.dup
    pairs1.each do |pair|
      if found = pairs2.index(pair)
        size += 1
        pairs2.delete_at found
      end
    end
    size
  end
end

class Class
  initializer_name             = 'initialize'
  initializer_spelling_checker = StringSimilarityChecker.new initializer_name

  # Raise error if a new method is similar but not identical to "initialize".
  # WARNING this is not something you should actually use in your apps.
  define_method(:method_added) do |name|
    name = name.to_s
    if name != initializer_name and initializer_spelling_checker =~ name
      raise "method name too similar to 'initialize': '#{name}'"
    end
  end
end

class ThisWorks
  def initialize  # properly spelled method
  end

  def init        # valid method name
  end
end

class ThisFails
  def initializer # wrong name
  end
end

class ThisAlsoFails
  def initilize   # spelling error
  end
end