Lisbn.extract()

lib/lisbn/lisbn.rb

@@ -1,4 +1,21 @@
 class Lisbn < String
+
+  # Find an ISBN in a string of text
+  def scan_isbns
+    scan(/([\dX-]{10,})/i).flatten.map do |match|
+      isbn = self.class.new(match)
+      if isbn.valid?
+        if block_given?
+          yield isbn
+        else
+          isbn
+        end
+      else
+        nil
+      end
+    end.compact
+  end
+
   # Returns a normalized ISBN form
   def isbn
     upcase.gsub(/[^0-9X]/, '')

spec/lisbn_spec.rb

@@ -132,4 +132,28 @@
       subject.split("7").should == ["9", "80000000002"]
     end
   end
+
+  describe "#scan_isbns" do
+    it "should find two ISBN-13s in this sentence and return an array" do
+      isbns = Lisbn.new("Hi, I'm looking for 9780000000002 or 978-601-7002-01-5.").scan_isbns
+      isbns.should be_kind_of Array
+      isbns.size.should == 2
+      isbns[0].should == "9780000000002"
+      isbns[1].isbn.should == "9786017002015"
+    end
+
+    it "should take a block" do
+      isbns = 0
+      Lisbn.new("Hi, I'm looking for 9780000000002 or 978-601-7002-01-5.").scan_isbns do |isbn|
+        isbn.should be_kind_of Lisbn
+        isbns += 1
+      end
+      isbns.should == 2
+    end
+
+    it "should return an empty array when no ISBNs are present" do
+      Lisbn.new("nothing to see here").scan_isbns.should == []
+    end
+  end
+
 end