{-# LANGUAGE DuplicateRecordFields #-} {-# LANGUAGE FlexibleInstances #-} {-# LANGUAGE OverloadedLabels #-} {-# LANGUAGE OverloadedLists #-} {-# LANGUAGE OverloadedStrings #-} module Person3 where import Control.Applicative import Data.Generics.Labels () import Person import Person2 import Schemas -- | v3 adds recursive field 'spouse', which leads to cycles data Person3 = Person3 { name :: String , age :: Int , addresses :: [String] , spouse :: Maybe Person3 , religion :: Maybe Religion , education :: [Education] } deriving (Eq, Show) instance HasSchema Person3 where schema = named "Person3" $ record $ Person3 <$> field "name" Person3.name <*> field "age" Person3.age <*> field "addresses" Person3.addresses <*> optField "spouse" Person3.spouse <*> optField "religion" Person3.religion <*> (field "studies" Person3.education <|> field "education" Person3.education) laura3, pepe3 :: Person3 -- pepe3 has a cycle with laura3 pepe3 = Person3 "Pepe" 38 ["2 Edward Square", "La Mar 10"] (Just laura3) Nothing [PhD "Computer Science", Degree "Engineering"] -- laura3 has a cycle with pepe3 laura3 = pepe3 { name = "Laura" , spouse = Just pepe3 , education = [Degree "English"] , addresses = ["2 Edward Square"] , religion = Just Catholic } -- >>> import qualified Data.ByteString.Lazy.Char8 as B -- >>> import Data.Aeson.Encode.Pretty -- >>> B.putStrLn $ encodePretty $ finiteEncode 4 laura3 -- { -- "L": { -- "spouse": { -- "L": {} -- }, -- "religion": "Catholic", -- "addresses": [ -- "2 Edward Square" -- ], -- "age": 38, -- "studies": { -- "Degree": "English" -- }, -- "name": "Laura" -- } -- } -- Unpacking infinite data is not supported currently -- >>> decode @Person3 (finiteEncode 4 pepe3) -- Left (MissingRecordField {name = "name", context = ["spouse"]})