Push State Machine: main thread sometimes gets stuck when accessing Local Device

Source/ARTPush.m

@@ -15,7 +15,8 @@
 #import "ARTJsonLikeEncoder.h"
 #import "ARTEventEmitter.h"
 #if TARGET_OS_IOS
-#import "ARTPushActivationStateMachine.h"
+#import <UIKit/UIKit.h>
+#import "ARTPushActivationStateMachine+Private.h"
 #endif
 #import "ARTPushAdmin.h"
 #import "ARTPushActivationEvent.h"
@@ -55,7 +56,6 @@ - (ARTPushActivationStateMachine *)activationMachine {
     return activationMachineInstance;
 }
 
-
 + (void)didRegisterForRemoteNotificationsWithDeviceToken:(NSData *)deviceTokenData rest:(ARTRest *)rest {
     // HEX string, i.e.: <12ce7dda 8032c423 8f8bd40f 3484e5bb f4698da5 8b7fdf8d 5c55e0a2 XXXXXXXX>
     // Normalizing token by removing symbols and spaces, i.e.: 12ce7dda8032c4238f8bd40f3484e5bbf4698da58b7fdf8d5c55e0a2XXXXXXXX
@@ -87,11 +87,29 @@ + (void)didFailToRegisterForRemoteNotificationsWithError:(NSError *)error realti
 }
 
 - (void)activate {
-    [[self activationMachine] sendEvent:[ARTPushActivationEventCalledActivate new]];
+    if (!self.activationMachine.delegate) {
+        dispatch_async(dispatch_get_main_queue(), ^{
+            // -[UIApplication delegate] is an UI API call
+            self.activationMachine.delegate = UIApplication.sharedApplication.delegate;
+            [self.activationMachine sendEvent:[ARTPushActivationEventCalledActivate new]];
+        });
+    }
+    else {
+        [self.activationMachine sendEvent:[ARTPushActivationEventCalledActivate new]];
+    }
 }
 
 - (void)deactivate {
-    [[self activationMachine] sendEvent:[ARTPushActivationEventCalledDeactivate new]];
+    if (!self.activationMachine.delegate) {
+        dispatch_async(dispatch_get_main_queue(), ^{
+            // -[UIApplication delegate] is an UI API call
+            self.activationMachine.delegate = UIApplication.sharedApplication.delegate;
+            [self.activationMachine sendEvent:[ARTPushActivationEventCalledDeactivate new]];
+        });
+    }
+    else {
+        [self.activationMachine sendEvent:[ARTPushActivationEventCalledDeactivate new]];
+    }
 }
 
 #endif

Source/ARTPushActivationStateMachine.m

@@ -22,7 +22,6 @@
 #import "ARTNSMutableRequest+ARTPush.h"
 
 #if TARGET_OS_IOS
-#import <UIKit/UIKit.h>
 
 NSString *const ARTPushActivationCurrentStateKey = @"ARTPushActivationCurrentState";
 NSString *const ARTPushActivationPendingEventsKey = @"ARTPushActivationPendingEvents";
@@ -133,16 +132,7 @@ - (void)deviceRegistration:(ARTErrorInfo *)error {
     #if TARGET_OS_IOS
     ARTLocalDevice *local = _rest.device_nosync;
 
-    __block id delegate;
-    if (self.delegate) {
-        delegate = self.delegate;
-    }
-    else {
-        dispatch_sync(_userQueue, ^{
-            // -[UIApplication delegate] is an UI API call
-            delegate = UIApplication.sharedApplication.delegate;
-        });
-    }
+    __block id delegate = self.delegate;
 
     if (![delegate conformsToProtocol:@protocol(ARTPushRegistererDelegate)]) {
         [NSException raise:@"ARTPushRegistererDelegate must be implemented on AppDelegate" format:@""];
@@ -202,16 +192,7 @@ - (void)deviceUpdateRegistration:(ARTErrorInfo *)error {
     #if TARGET_OS_IOS
     ARTLocalDevice *local = _rest.device_nosync;
 
-    __block id delegate;
-    if (self.delegate) {
-        delegate = self.delegate;
-    }
-    else {
-        dispatch_sync(_userQueue, ^{
-            // -[UIApplication delegate] is an UI API call
-            delegate = UIApplication.sharedApplication.delegate;
-        });
-    }
+    __block id delegate = self.delegate;
 
     if (![delegate conformsToProtocol:@protocol(ARTPushRegistererDelegate)]) {
         [NSException raise:@"ARTPushRegistererDelegate must be implemented on AppDelegate" format:@""];
@@ -278,16 +259,7 @@ - (void)deviceUnregistration:(ARTErrorInfo *)error {
     #if TARGET_OS_IOS
     ARTLocalDevice *local = _rest.device_nosync;
 
-    __block id delegate;
-    if (self.delegate) {
-        delegate = self.delegate;
-    }
-    else {
-        dispatch_sync(_userQueue, ^{
-            // -[UIApplication delegate] is an UI API call
-            delegate = UIApplication.sharedApplication.delegate;
-        });
-    }
+    __block id delegate = self.delegate;
 
     // Custom register
     SEL customDeregisterMethodSelector = @selector(ablyPushCustomDeregister:deviceId:callback:);
@@ -334,64 +306,43 @@ - (void)deviceUnregistration:(ARTErrorInfo *)error {
 
 - (void)callActivatedCallback:(ARTErrorInfo *)error {
     #if TARGET_OS_IOS
-dispatch_async(_userQueue, ^{
-    id delegate;
-    if (self.delegate) {
-        delegate = self.delegate;
-    }
-    else {
-        delegate = UIApplication.sharedApplication.delegate;
-    }
-
-    if ([delegate conformsToProtocol:@protocol(ARTPushRegistererDelegate)]) {
-        SEL activateCallbackMethodSelector = @selector(didActivateAblyPush:);
-        if ([delegate respondsToSelector:activateCallbackMethodSelector]) {
-            [delegate didActivateAblyPush:error];
+    dispatch_async(_userQueue, ^{
+        id delegate = self.delegate;
+        if ([delegate conformsToProtocol:@protocol(ARTPushRegistererDelegate)]) {
+            SEL activateCallbackMethodSelector = @selector(didActivateAblyPush:);
+            if ([delegate respondsToSelector:activateCallbackMethodSelector]) {
+                [delegate didActivateAblyPush:error];
+            }
         }
-    }
-});
+    });
     #endif
 }
 
 - (void)callDeactivatedCallback:(ARTErrorInfo *)error {
     #if TARGET_OS_IOS
-dispatch_async(_userQueue, ^{
-    id delegate;
-    if (self.delegate) {
-        delegate = self.delegate;
-    }
-    else {
-        delegate = UIApplication.sharedApplication.delegate;
-    }
-
-    if ([delegate conformsToProtocol:@protocol(ARTPushRegistererDelegate)]) {
-        SEL deactivateCallbackMethodSelector = @selector(didDeactivateAblyPush:);
-        if ([delegate respondsToSelector:deactivateCallbackMethodSelector]) {
-            [delegate didDeactivateAblyPush:error];
+    dispatch_async(_userQueue, ^{
+        id delegate = self.delegate;
+        if ([delegate conformsToProtocol:@protocol(ARTPushRegistererDelegate)]) {
+            SEL deactivateCallbackMethodSelector = @selector(didDeactivateAblyPush:);
+            if ([delegate respondsToSelector:deactivateCallbackMethodSelector]) {
+                [delegate didDeactivateAblyPush:error];
+            }
         }
-    }
-});
+    });
     #endif
 }
 
 - (void)callUpdateFailedCallback:(nullable ARTErrorInfo *)error {
     #if TARGET_OS_IOS
-dispatch_async(_userQueue, ^{
-    id delegate;
-    if (self.delegate) {
-        delegate = self.delegate;
-    }
-    else {
-        delegate = UIApplication.sharedApplication.delegate;
-    }
-
-    if ([delegate conformsToProtocol:@protocol(ARTPushRegistererDelegate)]) {
-        SEL updateFailedCallbackMethodSelector = @selector(didAblyPushRegistrationFail:);
-        if ([delegate respondsToSelector:updateFailedCallbackMethodSelector]) {
-            [delegate didAblyPushRegistrationFail:error];
+    dispatch_async(_userQueue, ^{
+        id delegate = self.delegate;
+        if ([delegate conformsToProtocol:@protocol(ARTPushRegistererDelegate)]) {
+            SEL updateFailedCallbackMethodSelector = @selector(didAblyPushRegistrationFail:);
+            if ([delegate respondsToSelector:updateFailedCallbackMethodSelector]) {
+                [delegate didAblyPushRegistrationFail:error];
+            }
         }
-    }
-});
+    });
     #endif
 }
 

Source/ARTRest.m

@@ -686,7 +686,7 @@ - (ARTLocalDevice *)device {
 // Store address of once_token to access it in debug function.
 static dispatch_once_t *device_once_token;
 
-- (NSString *)device_nosync {
+- (ARTLocalDevice *)device_nosync {
     static dispatch_once_t once;
     device_once_token = &once;
     static id device;