diff --git a/fields-json.cabal b/fields-json.cabal
--- a/fields-json.cabal
+++ b/fields-json.cabal
@@ -1,8 +1,8 @@
 Name:                fields-json
-Version:             0.2.2
-Synopsis: Abusing monadic syntax JSON objects generation.            
+Version:             0.2.2.2
+Synopsis: Abusing monadic syntax JSON objects generation.
 
-Description: 
+Description:
   Generation of big, complex JSON objects with Text.JSON is painful. And autoderivation is not always posible.
   Check documentation of Text.JSON.Gen for more info.
 
@@ -17,13 +17,13 @@
 
 
 library
-  exposed-modules: 
+  exposed-modules:
      Text.JSON.Gen
      Text.JSON.ToJSValue
      Text.JSON.FromJSValue
      Text.JSON.JSValueContainer
 
-  hs-source-dirs: src 
+  hs-source-dirs: src
   GHC-Options: -Wall
   build-depends: base >= 4 && < 5
   build-depends: json >= 0.4.4
diff --git a/src/Text/JSON/FromJSValue.hs b/src/Text/JSON/FromJSValue.hs
--- a/src/Text/JSON/FromJSValue.hs
+++ b/src/Text/JSON/FromJSValue.hs
@@ -15,6 +15,8 @@
 module Text.JSON.FromJSValue (
                                -- * Basic Parsing
                                  FromJSValue(..)
+                               , FromJSValueWithUpdate(..)
+                               , MatchWithJSValue(..)
                                -- * Data Extraction
                                , jsValueField
                                , fromJSValueField
@@ -22,6 +24,7 @@
                                , fromJSValueFieldCustom
                                , fromJSValueCustomMany
                                , fromJSValueCustomList
+                               , fromJSValueManyWithUpdate
                                -- * Running
                                , withJSValue  ) where
 import Text.JSON
@@ -32,7 +35,7 @@
 import qualified Data.ByteString.Base64 as BASE64
 import Control.Monad.Identity
 import Data.Maybe
-
+import Data.List
 
 -- | Structures that can be 'parsed' from JSON. Instances must declare either 'fromJSValue' (parse directly from 'JSValue') or 'fromJSValueM' (uses 'MonadReader')
 class FromJSValue a where
@@ -41,6 +44,22 @@
     fromJSValueM :: (JSValueContainer c , MonadReader c m) => m (Maybe a)
     fromJSValueM = liftM fromJSValue askJSValue
 
+
+-- | Structures that can be 'parsed' from JSON if some structure for update is provided
+class FromJSValueWithUpdate a where
+    fromJSValueWithUpdate :: Maybe a -> JSValue -> Maybe a
+    fromJSValueWithUpdate ma j = runIdentity $ withJSValue j $ liftM (fromJSValueWithUpdateM ma) askJSValue
+    fromJSValueWithUpdateM :: (JSValueContainer c , MonadReader c m) =>  Maybe a  -> m (Maybe a)
+    fromJSValueWithUpdateM ma = liftM (fromJSValueWithUpdate ma) askJSValue
+
+-- | Structures that can be matched with JSValue
+class MatchWithJSValue a where
+    matchesWithJSValue :: a -> JSValue -> Bool
+    matchesWithJSValue a j = runIdentity $ withJSValue j $ liftM (matchesWithJSValueM a) askJSValue
+    matchesWithJSValueM :: (JSValueContainer c , MonadReader c m) =>  a  -> m Bool
+    matchesWithJSValueM a = liftM (matchesWithJSValue a) askJSValue
+
+
 -- ---------------------------------------------------------------------------
 -- Instances for basic datatypes
 --
@@ -74,9 +93,12 @@
 
     fromJSValue _ = Nothing
 
+
+-- | Parsing any Maybe always returns Just
 instance (FromJSValue a) => FromJSValue (Maybe a) where
-    fromJSValue = join . fromJSValue
+    fromJSValue = Just . fromJSValue
 
+
 instance (FromJSValue a, FromJSValue b) => FromJSValue (a,b) where
     fromJSValue (JSArray [a,b]) = do a' <- fromJSValue a
                                      b' <- fromJSValue b
@@ -100,7 +122,8 @@
                                                                             Just a  -> return (Just `fmap` fromJSValue a)
       fromObject _ = return Nothing
 
--- | Reading the value that is on some field. With field if current JSON is not object
+-- | Reading the value that is on some field. With fail if current JSON is not object.
+-- | It can be ussed with 'Maybe a'. In such case Nothing will be returned iif field was not set.
 fromJSValueField ::  (JSValueContainer c , MonadReader c m, FromJSValue a) => String -> m (Maybe a)
 fromJSValueField s = liftM fromObject askJSValue
     where
@@ -121,7 +144,7 @@
     case mobj of
          Just obj -> local (setJSValue obj) (digger)
          Nothing -> return Nothing
-         
+
 -- | Runs parser on each element of underlaying json. Returns Just iff JSON is array.
 fromJSValueCustomMany :: (JSValueContainer c , MonadReader c m) => m (Maybe a) -> m (Maybe [a])
 fromJSValueCustomMany digger = fromJSValueCustomList (repeat digger)
@@ -144,7 +167,27 @@
                          _ -> return Nothing
                  _ -> return Nothing
          runDiggers _ _ = return $ Just []
-         
+
+
+-- | Runs parser on each element of underlaying json. Returns Just iff JSON is array.
+fromJSValueManyWithUpdate :: (JSValueContainer c , MonadReader c m, FromJSValueWithUpdate a, MatchWithJSValue a) => [a] -> m (Maybe [a])
+fromJSValueManyWithUpdate values = do
+    mjs <- fromJSValueM
+    case mjs of
+         Nothing -> return Nothing
+         Just js -> runFromJSValueAndUpdate js
+    where
+         runFromJSValueAndUpdate (j:js)=  do
+             mres <- local (setJSValue j) (fromJSValueWithUpdateM (find (\v -> matchesWithJSValue v j) values))
+             case mres of
+                 Just res -> do
+                     mress <- runFromJSValueAndUpdate js
+                     case mress of
+                         Just ress -> return $ Just (res:ress)
+                         _ -> return Nothing
+                 _ -> return Nothing
+         runFromJSValueAndUpdate [] = return $ Just []
+
 -- ----------------------------------------------------------------
 -- | Simple runner
 withJSValue :: (Monad m) => JSValue -> ReaderT JSValue m a -> m a