new files

Task/Delegates/Ruby/delegates-1.rb

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+class Delegator
+   attr_accessor :delegate
+   def operation
+      if @delegate.respond_to?(:thing)
+         @delegate.thing
+      else
+         'default implementation'
+      end
+   end
+end
+
+class Delegate
+   def thing
+      'delegate implementation'
+   end
+end
+
+if __FILE__ == $PROGRAM_NAME
+
+   # No delegate
+   a = Delegator.new
+   puts a.operation # prints "default implementation"
+
+   # With a delegate that does not implement "thing"
+   a.delegate = 'A delegate may be any object'
+   puts a.operation # prints "default implementation"
+
+   # With delegate that implements "thing"
+   a.delegate = Delegate.new
+   puts a.operation # prints "delegate implementation"
+end