| Safe Haskell | None |
|---|---|
| Language | Haskell2010 |
Opaleye.Field
Synopsis
- type family Field_ (a :: Nullability) b
- data Nullability
- type FieldNullable a = Field_ Nullable a
- type Field a = Field_ NonNullable a
- null :: FieldNullable a
- isNull :: FieldNullable a -> Field PGBool
- matchNullable :: Field_ NonNullable b -> (Field_ NonNullable a -> Field_ NonNullable b) -> Field_ Nullable a -> Field_ NonNullable b
- fromNullable :: Field_ NonNullable a -> Field_ Nullable a -> Field_ NonNullable a
- toNullable :: Field_ NonNullable a -> Field_ Nullable a
- maybeToNullable :: Maybe (Field_ NonNullable a) -> Field_ Nullable a
Documentation
type family Field_ (a :: Nullability) b #
Instances
| type Field_ NonNullable a # | |
Defined in Opaleye.Field | |
| type Field_ Nullable a # | |
Defined in Opaleye.Field | |
data Nullability #
Constructors
| NonNullable | |
| Nullable |
Instances
| type A (H HT :: Arr Type (C k2) k2) (C ((,,) h o NN) :: C k2) # | |
| type A (H NullsT :: Arr Type (TC a) k2) (TC ((,) t b) :: TC a) # | |
| type A (H WT :: Arr Type (TC a) k2) (TC ((,) t Req) :: TC a) # | |
| type A (H OT :: Arr Type (TC a) k2) (TC ((,) t b) :: TC a) # | |
| type A (H HT :: Arr Type (TC a) k2) (TC ((,) t b) :: TC a) # | |
| type A (H WT :: Arr Type (TC a) Type) (TC ((,) t Opt) :: TC a) # | |
| type A (H NullsT :: Arr Type (C Type) Type) (C ((,,) h o NN) :: C Type) # | |
| type A (H OT :: Arr Type (C Type) Type) (C ((,,) h o N) :: C Type) # | |
| type A (H OT :: Arr Type (C Type) Type) (C ((,,) h o NN) :: C Type) # | |
| type A (H HT :: Arr Type (C Type) Type) (C ((,,) h o N) :: C Type) # | |
type FieldNullable a = Field_ Nullable a #
type Field a = Field_ NonNullable a #
null :: FieldNullable a #
A NULL of any type
isNull :: FieldNullable a -> Field PGBool #
TRUE if the value of the column is NULL, FALSE otherwise.
Arguments
| :: Field_ NonNullable b | |
| -> (Field_ NonNullable a -> Field_ NonNullable b) | |
| -> Field_ Nullable a | |
| -> Field_ NonNullable b |
If the Field 'Nullable a is NULL then return the Field
'NonNullable b otherwise map the underlying Field 'Nullable a
using the provided function.
The Opaleye equivalent of maybe.
Will be generalized to Field_ n b in a later version.
Arguments
| :: Field_ NonNullable a | |
| -> Field_ Nullable a | |
| -> Field_ NonNullable a |
If the Field 'Nullable a is NULL then return the provided
Field 'NonNullable a otherwise return the underlying Field
'NonNullable a.
The Opaleye equivalent of fromMaybe and very similar
to PostgreSQL's COALESCE.
Will be generalized to Field_ n a in a later version.
toNullable :: Field_ NonNullable a -> Field_ Nullable a #
Treat a field as though it were nullable. This is always safe.
The Opaleye equivalent of Just.
Will be generalized to Field_ n a in a later version.
maybeToNullable :: Maybe (Field_ NonNullable a) -> Field_ Nullable a #
If the argument is Nothing return NULL otherwise return the
provided value coerced to a nullable type.
Will be generalized to Maybe (Field_ n a) in a later version.