first class changes

class_book.rb

@@ -0,0 +1,35 @@
+class Book
+    attr_reader :title, :price 
+    attr_writer :title, :price
+    def initialize(title=nil,price=nil)
+        if title.nil? || title.empty?
+            raise ArgumentError.new("Invalid string")
+        end
+        if price.nil? || price<0
+            raise ArgumentError.new("Invalid price")  
+        end
+        @title=title
+        @price=price
+    end
+
+    def formatted_price
+        if @price.integer?
+            return "#{@price} dollars"
+        else
+            conv = @price.to_s.split('.')
+            int_part = conv.first.to_i
+            dec_part = conv.last.to_i
+            if int_part == 0 
+                return "#{dec_part} cents"
+            end
+            return "#{int_part} dollars and #{dec_part} cents"
+        end
+    end
+
+end
+
+
+object = Book.new(' ',10.05)
+puts object.formatted_price
+
+