Updated EventKit example app to asynchronously fetch events from the …

…EKEventStore using a GCD queue.
alanthonyc · Jul 12, 2010 · a6a06b5 · a6a06b5
1 parent 522dd6c
commit a6a06b5
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Showing 2 changed files with 26 additions and 8 deletions.
diff --git a/Examples/NativeCal/Classes/EventKitDataSource.h b/Examples/NativeCal/Classes/EventKitDataSource.h
@@ -4,14 +4,16 @@
  */
 
 #import "Kal.h"
+#import <dispatch/dispatch.h>
 
 @class EKEventStore, EKEvent;
 
 @interface EventKitDataSource : NSObject <KalDataSource>
 {
-  EKEventStore *eventStore;
-  NSMutableArray *items;
-  NSMutableArray *events;
+  NSMutableArray *items;            // The list of events corresponding to the currently selected day in the calendar. These events are used to configure cells vended by the UITableView below the calendar month view.
+  NSMutableArray *events;           // Must be used on the main thread
+  EKEventStore *eventStore;         // Must be used on a background thread managed by eventStoreQueue
+  dispatch_queue_t eventStoreQueue; // Serializes access to eventStore and offloads the query work to a background thread.
 }
 
 + (EventKitDataSource *)dataSource;

diff --git a/Examples/NativeCal/Classes/EventKitDataSource.m b/Examples/NativeCal/Classes/EventKitDataSource.m
@@ -29,6 +29,7 @@ - (id)init
     eventStore = [[EKEventStore alloc] init];
     events = [[NSMutableArray alloc] init];
     items = [[NSMutableArray alloc] init];
+    eventStoreQueue = dispatch_queue_create("com.thepolypeptides.nativecalexample", NULL);
     [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(eventStoreChanged:) name:EKEventStoreChangedNotification object:nil];
   }
   return self;
@@ -52,6 +53,7 @@ - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(N
   UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:identifier];
   if (!cell) {
     cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:identifier] autorelease];
+    cell.accessoryType = UITableViewCellAccessoryDisclosureIndicator;
     cell.selectionStyle = UITableViewCellSelectionStyleNone;
     cell.imageView.contentMode = UIViewContentModeScaleAspectFill;
   }
@@ -70,25 +72,36 @@ - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger
 
 - (void)presentingDatesFrom:(NSDate *)fromDate to:(NSDate *)toDate delegate:(id<KalDataSourceCallbacks>)delegate
 {
+  // asynchronous callback on the main thread
   [events removeAllObjects];
-  NSLog(@"Fetching events from EventKit between %@ and %@...", fromDate, toDate);
-  NSPredicate *predicate = [eventStore predicateForEventsWithStartDate:fromDate endDate:toDate calendars:nil];
-  [events addObjectsFromArray:[eventStore eventsMatchingPredicate:predicate]];
-  [delegate loadedDataSource:self];
+  NSLog(@"Fetching events from EventKit between %@ and %@ on a GCD-managed background thread...", fromDate, toDate);
+  dispatch_async(eventStoreQueue, ^{
+    NSDate *fetchProfilerStart = [NSDate date];
+    NSPredicate *predicate = [eventStore predicateForEventsWithStartDate:fromDate endDate:toDate calendars:nil];
+    NSArray *matchedEvents = [eventStore eventsMatchingPredicate:predicate];
+    dispatch_async(dispatch_get_main_queue(), ^{
+      NSLog(@"Fetched %d events in %f seconds", [matchedEvents count], -1.f * [fetchProfilerStart timeIntervalSinceNow]);
+      [events addObjectsFromArray:matchedEvents];
+      [delegate loadedDataSource:self];
+    });
+  });
 }
 
 - (NSArray *)markedDatesFrom:(NSDate *)fromDate to:(NSDate *)toDate
 {
+  // synchronous callback on the main thread
   return [[self eventsFrom:fromDate to:toDate] valueForKeyPath:@"startDate"];
 }
 
 - (void)loadItemsFromDate:(NSDate *)fromDate toDate:(NSDate *)toDate
 {
+  // synchronous callback on the main thread
   [items addObjectsFromArray:[self eventsFrom:fromDate to:toDate]];
 }
 
 - (void)removeAllItems
 {
+  // synchronous callback on the main thread
   [items removeAllObjects];
 }
 
@@ -107,9 +120,12 @@ - (NSArray *)eventsFrom:(NSDate *)fromDate to:(NSDate *)toDate
 - (void)dealloc
 {
   [[NSNotificationCenter defaultCenter] removeObserver:self name:EKEventStoreChangedNotification object:nil];
-  [eventStore release];
   [items release];
   [events release];
+  dispatch_sync(eventStoreQueue, ^{
+    [eventStore release];
+  });
+  dispatch_release(eventStoreQueue);
   [super dealloc];
 }