New Example

README.md

@@ -24,34 +24,4 @@ you need to define an instance for Encode.
 If you have some JSON, and you want to decode it into some data type,
 you need to define an instance for Decode.
 
-## Examples
-
-```purescript
-module Foo where
-
-  import Control.Identity
-  import Data.Argonaut
-  import Data.Either
-
-  data Foo = Foo
-    { foo :: String
-    , bar :: Number
-    }
-
-  instance showFoo :: Show Foo where
-    show (Foo f) = "Foo(" ++ show f.foo ++ ", " ++ show f.bar ++ ")"
-
-  instance decodeFoo :: DecodeJson Identity (Either String) Foo where
-    decodeJson (Identity json) = maybe (Left "Not a Foo.") Right $ do
-      obj <- toObject json
-      foo <- (M.lookup "foo" obj >>= toString)
-      bar <- (M.lookup "bar" obj >>= toNumber)
-      pure (Foo {foo: foo, bar: bar})
-
-  instance encodeFoo :: EncodeJson Identity Identity Foo where
-    encodeJson (Identity (Foo {foo = f, bar = b})) = Identity $ JsonObject $
-      M.fromList [Tuple "foo" $ JsonString f, Tuple "bar" $ JsonNumber b]
-```
-
-[508]: https://github.com/purescript/purescript/tree/508
 [argonaut]: http://argonaut.io/

examples/Examples/Data/Argonaut/Record.purs

@@ -0,0 +1,36 @@
+module Examples.Data.Argonaut.Record where
+
+  import Data.Argonaut ((~>), (:=), (.?), jsonEmptyObject, printJson)
+  import Data.Argonaut.Encode (EncodeJson, encodeJson)
+  import Data.Argonaut.Decode (DecodeJson, decodeJson)
+  import Data.Maybe (Maybe(..))
+
+  import Debug.Trace (print)
+
+  newtype Foo = Foo
+    { foo :: Maybe Number
+    , bar :: Maybe String
+    }
+
+  instance decodeJsonFoo :: DecodeJson Foo where
+    decodeJson json = do
+      obj <- decodeJson json
+      foo <- obj .? "foo"
+      bar <- obj .? "bar"
+      pure $ Foo {foo: foo, bar: bar}
+
+  instance encodeJsonFoo :: EncodeJson Foo where
+    encodeJson (Foo f)
+      =  "bar" := f.bar
+      ~> "foo" := f.foo
+      ~> jsonEmptyObject
+
+  instance showFoo :: Show Foo where
+    show (Foo f) = "Foo {foo: " ++ show f.foo ++ ", bar:" ++ show f.bar ++ "}"
+
+  foo :: Foo
+  foo = Foo {foo: Just 42, bar: Nothing}
+
+  main = do
+    print $ "raw foo is: " ++ show foo
+    print $ "encoded foo is: " ++ printJson (encodeJson foo)