I have a function that throws an error, in this function I have a inside a
closure that I need to throw the error from it's completion handler. Is that possible ?
Here is my code so far.
enum CalendarEventError: ErrorType {
case UnAuthorized
case AccessDenied
case Failed
}
func insertEventToDefaultCalendar(event :EKEvent) throws {
let eventStore = EKEventStore()
switch EKEventStore.authorizationStatusForEntityType(.Event) {
case .Authorized:
do {
try insertEvent(eventStore, event: event)
} catch {
throw CalendarEventError.Failed
}
case .Denied:
throw CalendarEventError.AccessDenied
case .NotDetermined:
eventStore.requestAccessToEntityType(EKEntityType.Event, completion: { (granted, error) -> Void in
if granted {
//insertEvent(eventStore)
} else {
//throw CalendarEventError.AccessDenied
}
})
default:
}
}
When you define closure that throws:
enum MyError: ErrorType {
case Failed
}
let closure = {
throw MyError.Failed
}
then type of this closure is () throws -> ()
and function that takes this closure as parameter must have the same parameter type:
func myFunction(completion: () throws -> ()) {
}
It this function you can call completion
closure synchronous:
func myFunction(completion: () throws -> ()) throws {
completion()
}
and you have to add throws
keyword to function signature or call completion with try!
:
func myFunction(completion: () throws -> ()) {
try! completion()
}
or asynchronous:
func myFunction(completion: () throws -> ()) {
dispatch_async(dispatch_get_main_queue(), { try! completion() })
}
In last case you will not be able to catch error.
So if completion
closure in eventStore.requestAccessToEntityType
method and the method itself does not have throws
in its signature or if completion
is called asynchronously then you can not throw
from this closure.
I suggest you the following implementation of your function that passes error to callback instead of throwing it:
func insertEventToDefaultCalendar(event: EKEvent, completion: CalendarEventError? -> ()) {
let eventStore = EKEventStore()
switch EKEventStore.authorizationStatusForEntityType(.Event) {
case .Authorized:
do {
try insertEvent(eventStore, event: event)
} catch {
completion(CalendarEventError.Failed)
}
case .Denied:
completion(CalendarEventError.AccessDenied)
case .NotDetermined:
eventStore.requestAccessToEntityType(EKEntityType.Event, completion: { (granted, error) -> Void in
if granted {
//insertEvent(eventStore)
} else {
completion(CalendarEventError.AccessDenied)
}
})
default:
}
}