             "release":              "releaseDate",
             "track_count":          "trackCount",
             "collection":           "collectionID",
-        ]
-        
-        mixtapeMap.addAttributeMappingsFromDictionary(mixtapeAttributeMap)
+            ]
+        )
         
         let mixtapeList = RKResponseDescriptor(
-            mapping: mixtapeMap,
+            mapping: mixtapeMapping,
             method: .GET,
             pathPattern: Path.Mixtape.List(),
             keyPath: "results",

        objectManager.addResponseDescriptor(mixtapeList)
        
        let mixtapeDetail = RKResponseDescriptor(
            mapping: mixtapeMap,
            method: .GET,
            pathPattern: Path.Mixtape.Detail(),
            keyPath: nil,

            "artwork_credit_url":   "artworkCreditURL",
            "created":              "createdDate",
            "mixtape_count":        "mixtapeCount",
            ]
        )
        
        let collectionList = RKResponseDescriptor(
            mapping: collectionMapping,
            method: .GET,
            pathPattern: Path.Collection.List(),
            keyPath: "results",
