SyncIO

Materializes any sequenced exceptions into value space, where they may be handled.

This is analogous to the catch clause in try/catch, being the inverse of SyncIO.raiseError. Thus:

SyncIO.raiseError(ex).attempt.unsafeRunSync === Left(ex)

Returns a SyncIO action that treats the source task as the acquisition of a resource, which is then exploited by the use function and then released.

The bracket operation is the equivalent of the try {} catch {} finally {} statements from mainstream languages.

The bracket operation installs the necessary exception handler to release the resource in the event of an exception being raised during the computation.

If an exception is raised, then bracket will re-raise the exception ''after'' performing the release.

'''NOTE on error handling''': one big difference versus try/finally statements is that, in case both the release function and the use function throws, the error raised by use gets signaled.

For example:

 SyncIO("resource").bracket { _ =>
   // use
   SyncIO.raiseError(new RuntimeException("Foo"))
 } { _ =>
   // release
   SyncIO.raiseError(new RuntimeException("Bar"))
 }

In this case the error signaled downstream is "Foo", while the "Bar" error gets reported. This is consistent with the behavior of Haskell's bracket operation and NOT with try {} finally {} from Scala, Java or JavaScript.

Returns a new SyncIO task that treats the source task as the acquisition of a resource, which is then exploited by the use function and then released, with the possibility of distinguishing between normal termination and failure, such that an appropriate release of resources can be executed.

The bracketCase operation is the equivalent of try {} catch {} finally {} statements from mainstream languages when used for the acquisition and release of resources.

The bracketCase operation installs the necessary exception handler to release the resource in the event of an exception being raised during the computation.

In comparison with the simpler bracket version, this one allows the caller to differentiate between normal termination and termination in error. Note SyncIO does not support cancelation so that exit case should be ignored.

Monadic bind on SyncIO, used for sequentially composing two SyncIO actions, where the value produced by the first SyncIO is passed as input to a function producing the second SyncIO action.

Due to this operation's signature, flatMap forces a data dependency between two SyncIO actions, thus ensuring sequencing (e.g. one action to be executed before another one).

Any exceptions thrown within the function will be caught and sequenced in to the result SyncIO[B].

Executes the given finalizer when the source is finished, either in success or in error.

This variant of guaranteeCase evaluates the given finalizer regardless of how the source gets terminated:

• normal completion
• completion in error

This equivalence always holds:

 io.guarantee(f) <-> IO.unit.bracket(_ => io)(_ => f)

As best practice, it's not a good idea to release resources via guaranteeCase in polymorphic code. Prefer bracket for the acquisition and release of resources.

Executes the given finalizer when the source is finished, either in success or in error, allowing for differentiating between exit conditions.

This variant of guarantee injects an ExitCase in the provided function, allowing one to make a difference between:

• normal completion
• completion in error

This equivalence always holds:

 io.guaranteeCase(f) <-> IO.unit.bracketCase(_ => io)((_, e) => f(e))

As best practice, it's not a good idea to release resources via guaranteeCase in polymorphic code. Prefer bracketCase for the acquisition and release of resources.

Handle any error, potentially recovering from it, by mapping it to another SyncIO value.

Implements ApplicativeError.handleErrorWith.

Functor map on SyncIO. Given a mapping function, it transforms the value produced by the source, while keeping the SyncIO context.

Any exceptions thrown within the function will be caught and sequenced in to the result SyncIO[B].

Returns a new value that transforms the result of the source, given the recover or map functions, which get executed depending on whether the result ends in error or if it is successful.

This is an optimization on usage of attempt and map, this equivalence being true:

 io.redeem(recover, map) <-> io.attempt.map(_.fold(recover, map))

Usage of redeem subsumes handleError because:

 io.redeem(fe, id) <-> io.handleError(fe)

Returns a new value that transforms the result of the source, given the recover or bind functions, which get executed depending on whether the result ends in error or if it is successful.

This is an optimization on usage of attempt and flatMap, this equivalence being available:

 io.redeemWith(recover, bind) <-> io.attempt.flatMap(_.fold(recover, bind))

Usage of redeemWith subsumes handleErrorWith because:

 io.redeemWith(fe, F.pure) <-> io.handleErrorWith(fe)

Usage of redeemWith also subsumes flatMap because:

 io.redeemWith(F.raiseError, fs) <-> io.flatMap(fs)

Converts the source IO into any F type that implements the LiftIO type class.

Produces the result by running the encapsulated effects as impure side effects.

Any exceptions raised within the effect will be re-thrown during evaluation.

As the name says, this is an UNSAFE function as it is impure and performs side effects and throws exceptions. You should ideally only call this function once, at the very end of your program.