Dynamic Dispatch: Compare/Contrast

dynamic_dispatch_examples.rb

class DynamicMethodDispatchExample
  def do_something(what_to_do)
    begin
      self.send("provide_#{what_to_do}_string")
    rescue NoMethodError => ex
      raise ArgumentError
    end
  end

  def provide_foo_string
    FOO
  end

  def provide_bar_string
    BAR
  end

  def provide_baz_string
    BAZ
  end
end

class CaseStatementExample
  def do_something(what_to_do)
    case what_to_do.to_s
    when "foo"
      provide_foo_string
    when "bar"
      provide_bar_string
    when "baz"
      provide_baz_string
    else
      raise ArgumentError
    end
  end

  def provide_foo_string
    FOO
  end

  def provide_bar_string
    BAR
  end

  def provide_baz_string
    BAZ
  end
end

class ClassConstantLookupExample
  def do_something(what_to_do)
    provider_class = "#{self.class.name}::#{what_to_do.to_s.classify}Provider".constantize

    raise ArgumentError unless (provider_class < Provider)

    provider_class.new.provide_string
  end

  class Provider
    def provide_string
      raise "Unimplemented method."
    end
  end

  class FooProvider < Provider
    def provide_string
      FOO
    end
  end

  class BarProvider < Provider
    def provide_string
      BAR
    end
  end

  class BazProvider < Provider
    def provide_string
      BAZ
    end
  end
end

class ModuleConstantLookupExample
  def do_something(what_to_do)
    provider_module = "#{self.class.name}::#{what_to_do.to_s.classify}Provider".constantize
    do_something_with_provider(provider_module)
  end
  
  def do_something_with_provider(provider)
    raise ArgumentError unless provider.respond_to? :provide_string
    provider.provide_string
  end

  module FooProvider
    def self.provide_string
      FOO
    end
  end

  module BarProvider
    def self.provide_string
      BAR
    end
  end

  module BazProvider
    def self.provide_string
      BAZ
    end
  end
end