X-Git-Url: http://gitweb.michael.orlitzky.com/?a=blobdiff_plain;f=src%2FXml.hs;h=e8b7c4de311e0e90203dbda322e4bae2d2767676;hb=88b80555c3df3649799c8caa4de8d9c87c50be45;hp=c4d4049e2f5ec4fc62d93d80ab31d83e8d07c764;hpb=40ab1bcc0f1517ac9910928dd658c09195f50f12;p=dead%2Fhtsn-import.git

diff --git a/src/Xml.hs b/src/Xml.hs
index c4d4049..e8b7c4d 100644
--- a/src/Xml.hs
+++ b/src/Xml.hs
@@ -4,14 +4,13 @@
 --
 module Xml (
   DtdName(..),
-  ToFromXml(..),
+  FromXml(..),
   parse_opts,
   pickle_unpickle,
   unpickleable )
 where
 
 import Control.Exception ( SomeException(..), catch )
-import Database.Groundhog ( AutoKey )
 import Text.XML.HXT.Core (
   (>>>),
   (/>),
@@ -27,56 +26,42 @@ import Text.XML.HXT.Core (
   yes )
 
 
--- | A typeclass for types which can be converted into an associated
---   XML type. The story behind this is long, but basically, we need
---   to different types for each XML thingie we're going to import: a
---   database type and an XML type. Both Groundhog and HXT are very
---   particular about the types that they can use, and there's no way
---   to reuse e.g. a type that HXT can pickle in Groundhog. So this
---   typeclass gives us a way to get the XML type from the Groundhog
---   type.
+-- | A typeclass for XML types that can be converted into an
+--   associated database type. The story behind this is long, but
+--   basically, we need to different types most XML thingies we're
+--   going to import: a database type and an XML type.
 --
---   At first there appears to be an equally-valid approach, getting the
---   Groundhog type from the XML one. But Groundhog won't use type family
---   instances, so here we are.
+--   Both Groundhog and HXT are very particular about the types that
+--   they can use, and there's no way to reuse e.g. a type that HXT
+--   can pickle in Groundhog. This typeclass gives us a standard way
+--   to get the database type from the XML type that we have to define
+--   for HXT.
 --
-class ToFromXml a where
-  -- | Each instance a must declare its associated XML type (Xml a)
-  type Xml a :: *
-  type Container a :: *
+class FromXml a where
+  -- | Each instance @a@ must declare its associated database type @Db a@.
+  type Db a :: *
 
-  -- | And provide a function for getting an (Xml a) out of an "a."
-  to_xml :: a -> Xml a
+  -- | And provide a function for getting a @Db a@ out of an @a@.
+  from_xml :: a -> Db a
 
-  -- | And provide a function for getting an "a" out of an (Xml a).
-  from_xml :: Xml a -> a
 
-  -- | Often we need to provide a key to use as a foreign key into
-  --   some container. If the instance "belongs" to some other object,
-  --   then it might need to be passed a key before it can un-XML
-  --   itself. For example, the XML version of 'NewsTeam' doesn't
-  --   contain a message ID which is part of its database type.
-  from_xml_fk :: AutoKey (Container a) -> Xml a -> a
-  from_xml_fk _ = from_xml
-
-
--- | Represents the DTD filename ("SYSTEM") part of the DOCTYPE
+-- | Represents the DTD filename (\"SYSTEM\") part of the DOCTYPE
 --   definition.
 newtype DtdName = DtdName String
 
 -- | A list of options passed to 'readDocument' when we parse an XML
 --   document. All cosmetic whitespace should be removed, otherwise we
---   have to parse it in each pickler.
+--   would have to parse whitespace in each (un)pickler.
 --
 parse_opts :: SysConfigList
 parse_opts = [ withRemoveWS yes ]
 
 
 -- | Given a root element name and a file path, return both the
---   original unpickled root "object" and the one that was constructed
---   by pickled and unpickling the original. This is used in a number
---   of XML tests which pickle/unpickle and then make sure that the
---   output is the same as the input.
+--   original unpickled root \"object\" and the one that was
+--   constructed by pickled and unpickling the original. This is used
+--   in a number of XML tests which pickle/unpickle and then make sure
+--   that the output is the same as the input.
 --
 --   We return the object instead of an XmlTree (which would save us
 --   an unpickle call) because otherwise the type of @a@ in the call
@@ -118,6 +103,9 @@ pickle_unpickle root_element filepath = do
 --   would result. By taking the unpickler as an argument, we allow
 --   the caller to indirectly specify a concrete type.
 --
+--   Apologies the the name; unpickleable means \"we can unpickle
+--   it\", not \"not pickleable.\"
+--
 unpickleable :: XmlPickler a => FilePath -> PU a -> IO Bool
 unpickleable filepath unpickler = do
   xmldoc <- try_unpickle `catch` (\(SomeException _) -> return [])