| Safe Haskell | None |
|---|
Database.Persist.TH
Description
This module provides utilities for creating backends. Regular users do not need to use this module.
- persistWith :: PersistSettings -> QuasiQuoter
- persistUpperCase :: QuasiQuoter
- persistLowerCase :: QuasiQuoter
- persistFileWith :: PersistSettings -> FilePath -> Q Exp
- mkPersist :: MkPersistSettings -> [EntityDef SqlType] -> Q [Dec]
- data MkPersistSettings
- mpsBackend :: MkPersistSettings -> Type
- mpsGeneric :: MkPersistSettings -> Bool
- mkPersistSettings :: Type -> MkPersistSettings
- sqlSettings :: MkPersistSettings
- sqlOnlySettings :: MkPersistSettings
- mkMigrate :: Lift' a => String -> [EntityDef a] -> Q [Dec]
- mkSave :: String -> [EntityDef SqlType] -> Q [Dec]
- mkDeleteCascade :: MkPersistSettings -> [EntityDef a] -> Q [Dec]
- share :: [[EntityDef a] -> Q [Dec]] -> [EntityDef a] -> Q [Dec]
- derivePersistField :: String -> Q [Dec]
- persistFieldFromEntity :: MkPersistSettings -> EntityDef a -> Q [Dec]
Parse entity defs
persistWith :: PersistSettings -> QuasiQuoter
Converts a quasi-quoted syntax into a list of entity definitions, to be used as input to the template haskell generation code (mkPersist).
persistUpperCase :: QuasiQuoter
Apply persistWith to upperCaseSettings.
persistLowerCase :: QuasiQuoter
Apply persistWith to lowerCaseSettings.
persistFileWith :: PersistSettings -> FilePath -> Q Exp
Same as persistWith, but uses an external file instead of a
quasiquotation.
Turn EntityDefs into types
mkPersist :: MkPersistSettings -> [EntityDef SqlType] -> Q [Dec]
Create data types and appropriate PersistEntity instances for the given
EntityDefs. Works well with the persist quasi-quoter.
data MkPersistSettings
Settings to be passed to the mkPersist function.
mpsBackend :: MkPersistSettings -> Type
Which database backend we're using.
When generating data types, each type is given a generic version- which works with any backend- and a type synonym for the commonly used backend. This is where you specify that commonly used backend.
mpsGeneric :: MkPersistSettings -> Bool
Create generic types that can be used with multiple backends. Good for reusable code, but makes error messages harder to understand. Default: True.
Arguments
| :: Type | Value for |
| -> MkPersistSettings |
Create an MkPersistSettings with default values.
sqlSettings :: MkPersistSettings
Use the SqlPersist backend.
sqlOnlySettings :: MkPersistSettings
Same as sqlSettings, but set mpsGeneric to False.
Since 1.1.1
Various other TH functions
mkMigrate :: Lift' a => String -> [EntityDef a] -> Q [Dec]
Creates a single function to perform all migrations for the entities defined here. One thing to be aware of is dependencies: if you have entities with foreign references, make sure to place those definitions after the entities they reference.
mkSave :: String -> [EntityDef SqlType] -> Q [Dec]
Save the EntityDefs passed in under the given name.
mkDeleteCascade :: MkPersistSettings -> [EntityDef a] -> Q [Dec]
Generate a DeleteCascade instance for the given EntityDefs.
share :: [[EntityDef a] -> Q [Dec]] -> [EntityDef a] -> Q [Dec]
Apply the given list of functions to the same EntityDefs.
This function is useful for cases such as:
>>>share [mkSave "myDefs", mkPersist sqlSettings] [persistLowerCase|...|]
derivePersistField :: String -> Q [Dec]
Automatically creates a valid PersistField instance for any datatype
that has valid Show and Read instances. Can be very convenient for
Enum types.
persistFieldFromEntity :: MkPersistSettings -> EntityDef a -> Q [Dec]
produce code similar to the following:
instance PersistEntity e => PersistField e where toPersistValue = PersistMap $ zip columNames (map toPersistValue . toPersistFields) fromPersistValue (PersistMap o) = fromPersistValues $ map ((_,v) -> casefromPersistValue v of Left e -> error e Right r -> r) o fromPersistValue x = Left $ Expected PersistMap, received: ++ show x sqlType _ = SqlString