extracts succession logic

lib/prime_by_chain.rb

@@ -2,7 +2,7 @@
 
 class PrimeByChain
   def is_prime?(input)
-    return false if Processors::LessThanTwo.new.not_prime?(input)
+    return false if Processors::MAIN.new.not_prime?(input)
 
     return true
   end

lib/processors.rb

@@ -1,33 +1,34 @@
 module Processors
-  class LessThanTwo
+
+  class AbstractProcessor
+    def successor
+      EXECUTION_PLAN.fetch(self.class).call
+    end
+  end
+
+  class LessThanTwo < AbstractProcessor
     def not_prime?(number)
       if number < 2
         true
       else
         successor.not_prime?(number)
       end
     end
-
-    def successor
-      Processors::IsEven.new
-    end
   end
 
-  class IsEven
+  MAIN = LessThanTwo
+
+  class IsEven < AbstractProcessor
     def not_prime?(number)
       if number > 2 && number.even?
         true
       else
         successor.not_prime?(number)
       end
     end
-
-    def successor
-      Processors::HasSquareRoot.new
-    end
   end
 
-  class HasSquareRoot
+  class HasSquareRoot < AbstractProcessor
     def not_prime?(number)
       sqrt = Math.sqrt(number)
       if sqrt == sqrt.floor
@@ -36,13 +37,9 @@ def not_prime?(number)
         successor.not_prime?(number)
       end
     end
-
-    def successor
-      Processors::HasIntegerDivisor.new
-    end
   end
 
-  class HasIntegerDivisor
+  class HasIntegerDivisor < AbstractProcessor
     def not_prime?(number)
       if divisor_found?(number)
         true
@@ -51,10 +48,6 @@ def not_prime?(number)
       end
     end
 
-    def successor
-      Default.new
-    end
-
     private
 
     def divisor_found?(number)
@@ -70,4 +63,23 @@ def not_prime?(number)
       false
     end
   end
+
+  EXECUTION_PLAN = {
+    LessThanTwo       => -> do
+      IsEven.new
+    end,
+
+    IsEven            => -> do
+      Processors::HasSquareRoot.new
+    end,
+
+    HasSquareRoot     => -> do
+      Processors::HasIntegerDivisor.new
+    end,
+
+    HasIntegerDivisor => -> do
+      Default.new
+    end,
+  }
+
 end