         return nil
     }
     
-    private func filePath(key key: String) -> String
+    private func fileURLForKey(key key: String) -> NSURL
     {
         guard let directoryURL = self.documentsDirectoryURL()
         else

        
        if !success
        {
            let error = NSError(domain: "ArchiveStoreDomain", code: 2093, userInfo: [NSLocalizedDescriptionKey: "create file failed"])
            throw error
        }
    }
    
    func dataForKey(key: String) throws -> NSData?
    {
        let data = try NSData(contentsOfFile: self.filePath(key: key), options: [])
        
        return data
    }
    
    func deleteDataForKey(key: String) throws
    {
        try self.fileManager.removeItemAtPath(self.filePath(key: key))
    }
    
    private func documentsDirectoryURL() -> NSURL?

        
        let fileURL = directoryURL.URLByAppendingPathComponent("dontlookatthis-\(key).plist")
        
        return fileURL
    }
}