Opaleye.Field

Documentation

type family Field_ (a :: Nullability) b

Instances

type Field_ NonNullable a

type Field_ NonNullable a = Column a

type Field_ Nullable a

type Field_ Nullable a = Column (Nullable a)

data Nullability

Constructors

NonNullable

Nullable

Instances

type A * (TC a) k2 (H * (TC a) k2 NullsT) (TC a ((,) (a, a, Nullability) Optionality t b))

type A * (TC a) k2 (H * (TC a) k2 NullsT) (TC a ((,) (a, a, Nullability) Optionality t b)) = A * (C a) k2 (H * (C a) k2 NullsT) (C a t)

type A * (TC a) k2 (H * (TC a) k2 WT) (TC a ((,) (a, a, Nullability) Optionality t Req))

type A * (TC a) k2 (H * (TC a) k2 WT) (TC a ((,) (a, a, Nullability) Optionality t Req)) = A * (C a) k2 (H * (C a) k2 OT) (C a t)

type A * (TC a) k2 (H * (TC a) k2 OT) (TC a ((,) (a, a, Nullability) Optionality t b))

type A * (TC a) k2 (H * (TC a) k2 OT) (TC a ((,) (a, a, Nullability) Optionality t b)) = A * (C a) k2 (H * (C a) k2 OT) (C a t)

type A * (TC a) k2 (H * (TC a) k2 HT) (TC a ((,) (a, a, Nullability) Optionality t b))

type A * (TC a) k2 (H * (TC a) k2 HT) (TC a ((,) (a, a, Nullability) Optionality t b)) = A * (C a) k2 (H * (C a) k2 HT) (C a t)

type A * (C k2) k2 (H * (C k2) k2 HT) (C k2 ((,,) k2 k2 Nullability h o NN))

type A * (C k2) k2 (H * (C k2) k2 HT) (C k2 ((,,) k2 k2 Nullability h o NN)) = h

type A * (TC a) * (H * (TC a) * WT) (TC a ((,) (a, a, Nullability) Optionality t Opt))

type A * (TC a) * (H * (TC a) * WT) (TC a ((,) (a, a, Nullability) Optionality t Opt)) = Maybe (A * (C a) * (H * (C a) * OT) (C a t))

type A * (C *) * (H * (C *) * NullsT) (C * ((,,) * * Nullability h o NN))

type A * (C *) * (H * (C *) * NullsT) (C * ((,,) * * Nullability h o NN)) = Column (Nullable o)

type A * (C *) * (H * (C *) * OT) (C * ((,,) * * Nullability h o N))

type A * (C *) * (H * (C *) * OT) (C * ((,,) * * Nullability h o N)) = Column (Nullable o)

type A * (C *) * (H * (C *) * OT) (C * ((,,) * * Nullability h o NN))

type A * (C *) * (H * (C *) * OT) (C * ((,,) * * Nullability h o NN)) = Column o

type A * (C *) * (H * (C *) * HT) (C * ((,,) * * Nullability h o N))

type A * (C *) * (H * (C *) * HT) (C * ((,,) * * Nullability h o N)) = Maybe h

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.

matchNullable

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.

fromNullable

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.