Swift 3 adding #esaping attribute crashes when calling init in NSOperation - swift3

Question

I have a function that has defined a closure like this:
func synchronizeData(completion externalCompletion: RequestsCompletionHandler?) {
let closure = {
(operationCompletion:#escaping ()->Void) in
assert(Thread.isMainThread, "must be the main thread")
/*
Internal (non-optional) completion handler
*/
let internalCompletion: RequestsCompletionHandler = {
(success, newData, decommissionRequired, errors) -> Void in
/*
Synchronization is finished. Firstly, call either the external completion handler or the delegate
*/
if let externalCompletion = externalCompletion {
externalCompletion(success, newData, decommissionRequired, errors)
}
else {
self.delegate?.synchroniationInteractor(self, didSynchronizeDataWithStatus: success, dataIsNew: newData, decommissionRequired: decommissionRequired, error: errors.last)
}
/*
Now call the closure operation's completion handler
*/
operationCompletion()
}
/*
The synchronization itself
*/
guard let _ = self.keychain.retrieveActivationIdentifiers() else {
internalCompletion(false, false, false, [NSError(domain: "", code: 0, userInfo: ["reason" : "unable to retrieve credentials"])])
return
}
var errors :[NSError] = []
var numberOfRequests = 0
var completedRequests = 0
var decommissionRequired: Bool?
/*
Synchronization results handler. Regardless of success for fail, increase completed requests counter and append any errors to array, if final request call main completion block
*/
let handleCompletedRequests = {
(error: NSError?) -> Void in
// assert(NSThread.isMainThread(), "must be the main thread")
if let error = error {
errors.append(error)
}
completedRequests += 1
if(completedRequests >= numberOfRequests) {
internalCompletion(errors.count == 0, true, decommissionRequired, errors)
/*
Decrement operations counter
*/
self.manageBusy(retain: false)
}
}
/*
Increment operations counter
*/
self.manageBusy(retain: true)
/*
Do the actual synchronization.
Fetch the Patient Data first
*/
self.fetchPatientDataInternal {
(success, newData, error) -> Void in
numberOfRequests = 6
//Fetch Patient Schedule
self.fetchPatientScheduleInternal {
(success, newData, error) -> Void in
handleCompletedRequests(error)
}
//Fetch Patient Thresholds
self.fetchPatientThresholdInternal {
(success, newData, error) -> Void in
handleCompletedRequests(error)
}
//Fetch Patient Device Settings
self.fetchPatientDeviceSettingsInternal {
(success, newData, decommissionReq, error) -> Void in
decommissionRequired = decommissionReq
handleCompletedRequests(error)
}
// Device Checkin
self.deviceCheckInInternal {
(success, newData, error) -> Void in
handleCompletedRequests(error)
}
// Upload Vitals
self.uploadPendingVitalsInternal {
(success, newData, error) -> Void in
handleCompletedRequests(error)
}
//Upload Health sessions
self.uploadPendingHealthSessionsInternal {
(success, newData, error) -> Void in
handleCompletedRequests(error)
}
}
}
let operation = CIAsyncronousOperation.init(closure: closure as! (()->Void)-> Void)
operation.name = "Data Synchronization"
isolationQueue.addOperation(operation)
}
When we invoke this line in the above function i.e
let operation = CIAsyncronousOperation.init(closure: closure as! (()->Void)-> Void)
The application crashes with the following info:
0x00000001003b083c CIAppliance`partial apply forwarder for CIAppliance.SynchronizationInteractor.(synchronizeData (completion : Swift.Optional<(Swift.Bool, Swift.Optional, Swift.Optional, Swift.Array<__ObjC.NSError>) -> ()>) -> ()).(closure #1) at SynchronizationInteractor.swift
The CIAsyncronousOperation init is defined as follows:
init(closure aClosure: #escaping (()->Void)-> Void)
{
closure = aClosure
}
I am unable to find out the reason for the crash. Is it casting issue or due to the new Swift 3 syntax change?

Answer 1

If you are having to force cast the function then there is a good chance you have got the function signature incorrect. If CIAsyncronousOperation is defined as follows it will compile. Both the function and the function that is parameter aClosure need to be set as #escaping
class CIAsyncronousOperation {
init(closure aClosure: #escaping (#escaping ()->Void)->Void)
{
closure = aClosure
}
var closure : (#escaping ()->Void)-> Void;
}