Eliminate need for class eval

activerecord.rb

# lib/carrierwave/orm/activerecord.rb from jnicklas/carrierwave


# before
class_eval <<-RUBY, __FILE__, __LINE__+1
  def #{column}=(new_file)
    column = _mounter(:#{column}).serialization_column
    send(:"\#{column}_will_change!")
    super
  end

  def remote_#{column}_url=(url)
    column = _mounter(:#{column}).serialization_column
    send(:"\#{column}_will_change!")
    super
  end

  def remove_#{column}!
    super
    _mounter(:#{column}).remove = true
    _mounter(:#{column}).write_identifier
  end

  def serializable_hash(options=nil)
    hash = {}

    except = options && options[:except] && Array.wrap(options[:except]).map(&:to_s)
    only   = options && options[:only]   && Array.wrap(options[:only]).map(&:to_s)

    self.class.uploaders.each do |column, uploader|
      if (!only && !except) || (only && only.include?(column.to_s)) || (except && !except.include?(column.to_s))
        hash[column.to_s] = _mounter(column).uploader.serializable_hash
      end
    end
    super(options).merge(hash)
  end
RUBY

# after
define_method("#{column}=") do |new_file|
  serialization_column = _mounter(column.to_sym).serialization_column
  send(:"#{serialization_column}_will_change!")
  super
end

define_method("remote_#{column}_url=") do |url|
  serialization_column = _mounter(column.to_sym).serialization_column
  send(:"#{serialization_column}_will_change!")
  super
end

define_method("remove_#{column}!") do
  super
  _mounter(column.to_sym).remove = true
  _mounter(column.to_sym).write_identifier
end

def serializable_hash(options = nil)
  hash = {}

  except = options && options[:except] && Array.wrap(options[:except]).map(&:to_s)
  only   = options && options[:only]   && Array.wrap(options[:only]).map(&:to_s)

  self.class.uploaders.each do |column, uploader|
    if (!only && !except) || (only && only.include?(column.to_s)) || (except && !except.include?(column.to_s))
      hash[column.to_s] = _mounter(column).uploader.serializable_hash
    end
  end
  super(options).merge(hash)
end

connection.rb

# lib/faraday/connection.rb from technoweenie/faraday

# before
%w[get head delete].each do |method|
  class_eval <<-RUBY, __FILE__, __LINE__ + 1
    def #{method}(url = nil, params = nil, headers = nil)
      run_request(:#{method}, url, nil, headers) { |request|
        request.params.update(params) if params
        yield request if block_given?
      }
    end
  RUBY
end

# after
[:get, :head, :delete].each do |method|
  define_method(method) do |url = nil, params = nil, headers = nil|
    run_request(method, url, nil, headers) { |request|
      request.params.update(params) if params
      yield request if block_given?
    }
  end
end

http://tenderlovemaking.com/2013/03/03/dynamic_method_definitions.html