Indexable is an utility class used to derive instances of IResource

Example:

data Person= Person{ pname :: String, cars :: [DBRef Car]} deriving (Show, Read, Typeable)
data Car= Car{owner :: DBRef Person , cname:: String} deriving (Show, Read, Eq, Typeable)

Since Person and Car are instances of Read ans Show, by defining the Indexable instance will implicitly define the IResource instance for file persistence:

instance Indexable Person where  key Person{pname=n} = "Person " ++ n
instance Indexable Car where key Car{cname= n} = "Car " ++ n

Serialize is an alternative to the IResource class for defining persistence in TCache. The deserialization must be as lazy as possible. serialization/deserialization are not performance critical in TCache

Read, Show, instances are implicit instances of Serializable

   serialize  = pack . show
   deserialize= read . unpack

Since write and read to disk of to/from the cache are not be very frequent The performance of serialization is not critical.

Set the default persistence mechanism of all serializable objects that have setPersist= const Nothing. By default it is filePersist

this statement must be the first one before any other TCache call

Implements default default-persistence of objects in files with their keys as filenames

a persist mechanism has to implement these three primitives filePersist is the default file persistence