Just package:esqueleto

Analogous to Just, promotes a value of type typ into one of type Maybe typ. It should hold that val . Just === just . val. This function will try not to produce a nested Maybe. This is in accord with how SQL represents NULL. That means that just . just = just. This behavior was changed in v3.6.0.0. If you want to produce nested Maybe, see just'.

Like just, but this function does not try to collapse nested Maybe. This may be useful if you have type inference problems with just.

Same as just but for ValueList. Most of the time you won't need it, though, because you can use just from inside subList_select or Just from inside valList.

Same as belongsTo, but uses getJust and therefore is similarly unsafe.

Same as get, but for a non-null (not Maybe) foreign key. Unsafe unless your database is enforcing that the foreign key is valid.

Example usage

With schema-1 and dataset-1,

getJustSpj :: MonadIO m => ReaderT SqlBackend m User
getJustSpj = getJust spjId

spj <- getJust spjId

The above query when applied on dataset-1, will get this record:

+----+------+-----+
| id | name | age |
+----+------+-----+
|  1 | SPJ  |  40 |
+----+------+-----+

getJustUnknown :: MonadIO m => ReaderT SqlBackend m User
getJustUnknown = getJust unknownId

mrx <- getJustUnknown This just throws an error.

Same as getJust, but returns an Entity instead of just the record.

Example usage

With schema-1 and dataset-1,

getJustEntitySpj :: MonadIO m => ReaderT SqlBackend m (Entity User)
getJustEntitySpj = getJustEntity spjId

spjEnt <- getJustEntitySpj

The above query when applied on dataset-1, will get this entity:

+----+------+-----+
| id | name | age |
+----+------+-----+
|  1 | SPJ  |  40 |
+----+------+-----+