Composite.Opaleye.Update

Module which provides utilities for processing updates using Opaleye and Composite

Documentation

class RecordToUpdate (rs :: [*]) (ss :: [*])

Typeclass which allows transformation of a record from its select form to neutral update form, which boils down to wrapping fields that have defaults with Just.

Minimal complete definition

recordToUpdate

Instances

RecordToUpdate ([] :: [Type]) ([] :: [Type])

For an empty record, just act as id.

Defined in Composite.Opaleye.Update

Methods

recordToUpdate :: Record [] -> Record []

RecordToUpdate rs ss => RecordToUpdate (r ': rs) (r ': ss)

For a field whose type doesn't change between selection and update, just pass the field unchanged and then recurse.

Defined in Composite.Opaleye.Update

Methods

recordToUpdate :: Record (r ': rs) -> Record (r ': ss)

RecordToUpdate rs ss => RecordToUpdate ((s :-> a) ': rs) ((s :-> Maybe a) ': ss)

For a field whose type at selection is s :-> a but at update is s :-> Maybe a (a field which has a default value) add in a Just and recurse.

Defined in Composite.Opaleye.Update

Methods

recordToUpdate :: Record ((s :-> a) ': rs) -> Record ((s :-> Maybe a) ': ss)

recordToUpdate :: RecordToUpdate rs ss => Record rs -> Record ss

Transform a Record rs obtained from the database to a Record ss representing an updated version of the row.

Opaleye's runUpdate family of functions all take an update function of the type columnsR -> columnsW, which this function implements generically for a no-op update.

Typically this function is composed with one or more lens sets which update the fields after the transformation.