Support conversion of Clojure ratios to MongoDB data types

We go with doubles because it is the only realistic solution that is
interoperable with all other technologies. Plus, Clojure ratios are just
lazily evaluated doubles anyway.

src/monger/conversion.clj

@@ -23,7 +23,7 @@
 
 (ns monger.conversion
   (:import [com.mongodb DBObject BasicDBObject BasicDBList DBCursor]
-           [clojure.lang IPersistentMap Keyword]
+           [clojure.lang IPersistentMap Keyword Ratio]
            [java.util List Map Date]
            [org.bson.types ObjectId]))
 
@@ -39,6 +39,10 @@
   (to-db-object [input]
     input)
 
+  Ratio
+  (to-db-object [^Ratio input]
+    (double input))
+
   Keyword
   (to-db-object [^Keyword input] (.getName input))
 

test/monger/test/conversion.clj

@@ -26,6 +26,11 @@
         output (cnv/to-db-object input)]
     (is (= input output))))
 
+(deftest convert-rationale-to-dbobject
+  (let [input  11/2
+        output (cnv/to-db-object input)]
+    (is (= 5.5 output))))
+
 (deftest convert-string-to-dbobject
   (let [input  "MongoDB"
         output (cnv/to-db-object input)]

test/monger/test/inserting.clj

@@ -55,6 +55,13 @@
         result     (mgcol/insert "people" doc)]
     (is (= id (monger.util/get-id doc)))))
 
+(deftest insert-a-document-with-clojure-ratio-in-it
+  (let [collection "widgets"
+        id         (ObjectId.)
+        doc        { :ratio 11/2 "_id" id }
+        result     (mgcol/insert "widgets" doc)]
+    (is (= 5.5 (:ratio (mgcol/find-map-by-id collection id))))))
+
 
 
 ;;