Add the insert_xml_or_select function to TSN.XmlImport and use it in TSN.XML.News.

[dead/htsn-import.git] / src / TSN / XmlImport.hs

diff --git a/src/TSN/XmlImport.hs b/src/TSN/XmlImport.hs
index 3791ab56ef19add5ec4d0638d94a4e26cec51b51..4300e87ff4d6182475fcda1f30071b2082a43030 100644 (file)
--- a/src/TSN/XmlImport.hs
+++ b/src/TSN/XmlImport.hs
@@ -26,3 +26,18 @@ class (FromXml a, PersistEntity (Db a)) => XmlImport a where
                   => a
                   -> m ( Either (AutoKey (Db a)) (AutoKey (Db a)) )
   insertByAll_xml x = insertByAll (from_xml x)
+
+
+  -- | Try to insert the given object and get its primary key
+  --   back. Or, if there's a unique constraint violation, get the
+  --   primary key of the unique thing already present.
+  --
+  --   Note: we can switch to using fmap here as soon as Functor is a
+  --   superclass of Monad (PersistBackend is a Monad).
+  --
+  insert_xml_or_select :: (PersistBackend m)
+                       => a
+                       -> m (AutoKey (Db a))
+  insert_xml_or_select x = do
+    tmp <- insertByAll_xml x
+    return $ (either id id) tmp