A factory with no if statements inspired by Sandi Metz "Polly want a message" talk

Clump.rb

class Clump
  def initialize(spec:, input:)
    @spec = spec
    @possibilities = @input
  end

  def self.build(spec:, possibilities: [])
    descendants.detect { |klass| klass.match?(spec) }.new(spec: spec, input: possibilities).lines
  end

  def self.inherited?(klass)
    descendants.push klass
  end

  def self.descendants
    @descendants ||= []
  end
end

class Comment < Clump
  def self.match?(spec)
    spec.include?('#')
  end
  
  def lines
    #...etc...
  end
end

class LineNumber < Clump
  def self.match?(spec)
    true
  end
  
  def lines
    #...etc...
  end
  
  private

  def expand_clump
    #...etc...
  end
end

Sandi Metz gave a great presentation about OO design and polymorphism, using a Factory to refactor some code.

It inspired me to find a way to improve the Factory and remove the if statements completely.

This gist and the great article that goes with it were a help, most especially the posted by @mereghost.

Ref: https://apidock.com/ruby/v1_9_3_125/Class/inherited