Review changes for kvo cleanliness

MVMCoreUI/Alerts/MVMCoreAlertHandler+Extension.swift

@@ -12,19 +12,19 @@ public extension MVMCoreAlertHandler {
     
     /// Re-evaluates the queue operations
     @objc func reevaluteQueue() {
-        var highestReadyOperation: MVMCoreTopAlertOperation?
+        var higherPriorityOperationIsReady = false
         var executingOperation: MVMCoreTopAlertOperation?
+        let pageType = (MVMCoreUISplitViewController.main()?.getCurrentDetailViewController() as? MVMCoreViewControllerProtocol)?.pageType
         let sortedOperations = topAlertQueue.operations.sorted { $0.queuePriority.rawValue > $1.queuePriority.rawValue }
         for case let operation as MVMCoreTopAlertOperation in sortedOperations {
             guard !operation.isCancelled,
                   !operation.isFinished else { continue }
-            operation.refreshReady()
+            updatePageReadiness(for: operation, with: pageType)
-            if operation.isReady,
-               highestReadyOperation == nil {
-                highestReadyOperation = operation
-            }
             if operation.isExecuting {
                 executingOperation = operation
+            } else if operation.isReady,
+                      executingOperation == nil {
+                higherPriorityOperationIsReady = true
             }
         }
         guard let currentOperation = executingOperation else { return }
@@ -37,8 +37,7 @@ public extension MVMCoreAlertHandler {
         }
             
         // If the highest priority operation is not executing, and the executing operation is persistent, cancel it.
-        if let newOperation = highestReadyOperation,
+        if higherPriorityOperationIsReady,
-           currentOperation != newOperation,
            currentOperation.topAlertObject.persistent {
             currentOperation.reAddAfterCancel = true
             currentOperation.cancel()
@@ -50,6 +49,20 @@ public extension MVMCoreAlertHandler {
         NotificationCenter.default.addObserver(self, selector: #selector(viewControllerChanged(notification:)), name: NSNotification.Name(rawValue: MVMCoreNotificationViewControllerChanged), object: nil)
     }
     
+    /// Updates the operation isDisplayable based on the page type.
+    private func updatePageReadiness(for topOperation: MVMCoreTopAlertOperation, with pageType: String?) {
+        guard let pages = topOperation.topAlertObject.json?.optionalArrayForKey("pages") as? [String],
+              pages.count != 0 else {
+            topOperation.isDisplayable = true
+            return
+        }
+        guard let pageType = pageType else {
+            topOperation.isDisplayable = false
+            return
+        }
+        topOperation.isDisplayable = pages.contains(pageType)
+    }
+        
     /// When a detail page changes, check top alerts.
     @objc private func viewControllerChanged(notification: Notification) {
         reevaluteQueue()

MVMCoreUI/TopAlert/MVMCoreTopAlertOperation.h

@@ -15,6 +15,9 @@
 
 @property (readonly, getter=isPaused) BOOL paused;
 
+/// A bool for if this top alert can be displayed. It is only ready if true.
+@property (nonatomic, getter=isDisplayable) BOOL displayable;
+
 @property (nonatomic) BOOL reAddAfterCancel;
 
 @property (nonnull, nonatomic, strong) MVMCoreTopAlertObject *topAlertObject;
@@ -30,7 +33,4 @@
 // Unpauses the operation, resuming any alert.
 - (void)unpause;
 
-// NSOperationQueue uses KVO, this forces it to aknowledge changes
-- (void)refreshReady;
-
 @end

MVMCoreUI/TopAlert/MVMCoreTopAlertOperation.m

@@ -16,6 +16,7 @@
     __block BOOL _paused;
     __block BOOL _displayed;
     __block BOOL _animating;
+    __block BOOL _displayable;
 }
 
 @property (readwrite, getter=isPaused) BOOL paused;
@@ -26,6 +27,7 @@
 @property (strong, nonatomic) dispatch_queue_t pausedQueue;
 @property (strong, nonatomic) dispatch_queue_t displayedQueue;
 @property (strong, nonatomic) dispatch_queue_t animatingQueue;
+@property (strong, nonatomic) dispatch_queue_t displayableQueue;
 
 @property (nonatomic, strong) dispatch_source_t timerSource;
 
@@ -40,6 +42,8 @@
         self.pausedQueue = dispatch_queue_create("paused", DISPATCH_QUEUE_CONCURRENT);
         self.displayedQueue = dispatch_queue_create("displayed", DISPATCH_QUEUE_CONCURRENT);
         self.animatingQueue = dispatch_queue_create("animating", DISPATCH_QUEUE_CONCURRENT);
+        self.displayableQueue = dispatch_queue_create("displayable", DISPATCH_QUEUE_CONCURRENT);
+        self.displayable = YES;
     }
     return self;
 }
@@ -109,25 +113,35 @@
     });
 }
 
-// Ensure the current page is supported for this top alert.
+
+- (BOOL)isDisplayable {
+    __block BOOL isDisplayable;
+    dispatch_sync(self.displayableQueue, ^{
+        isDisplayable = self->_displayable;
+    });
+    return isDisplayable;
+}
+
+- (void)setDisplayable:(BOOL)displayable {
+    if (displayable != self.isDisplayable) {
+        BOOL isReady = [super isReady];
+        if (isReady) {
+            [self willChangeValueForKey:@"isReady"];
+        }
+        dispatch_barrier_async(self.displayableQueue, ^{
+            self->_displayable = displayable;
+        });
+        if (isReady) {
+            [self didChangeValueForKey:@"isReady"];
+        }
+    }
+}
+
 - (BOOL)isReady {
-    BOOL isReady = [super isReady];
+    if (self.isCancelled) {
-    if (self.isCancelled || self.isFinished) {
+        return [super isReady];
-        return isReady;
     }
-    
+    return [super isReady] && self.isDisplayable;
-    NSArray<NSString *> *pages = [self.topAlertObject.json array:@"pages"];
-    if (pages.count == 0) {
-        return isReady;
-    }
-    
-    UIViewController *detailViewController = [[MVMCoreUISplitViewController mainSplitViewController] getCurrentDetailViewController];
-    if (![detailViewController conformsToProtocol:@protocol(MVMCoreViewControllerProtocol)]) {
-        return isReady;
-    }
-    
-    NSString *pageType = ((UIViewController<MVMCoreViewControllerProtocol> *)detailViewController).pageType;
-    return isReady && [pages containsObject:pageType];
 }
 
 - (void)main {
@@ -254,11 +268,6 @@
     }
 }
 
-- (void)refreshReady {
-    [self willChangeValueForKey:@"isReady"];
-    [self didChangeValueForKey:@"isReady"];
-}
-
 #pragma mark - Delegate functions
              
 - (void)topAlertViewBeginAnimation {
@@ -278,6 +287,7 @@
     copyObject.topAlertObject = self.topAlertObject;
     copyObject.paused = self.paused;
     copyObject.reAddAfterCancel = self.reAddAfterCancel;
+    copyObject.displayable = self.isDisplayable;
     copyObject.queuePriority = self.queuePriority;
     for (NSOperation *dependency in self.dependencies) {
         [copyObject addDependency:dependency];