changesets.m

changesets.m

- (void) init {
    [super init];
    self.activityItemsTableChangeSignal = [[[RACSignal zip:@[[RACObserve(self, activityItems) ignore:nil],
                                                        [RACObserve(self, previousActivityItems) ignore:nil]]]
    skip:1]
    reduceEach:^id (NSOrderedSet *activityItems, NSOrderedSet *previousActivityItems){
        return [self generateChangeSetsForSection:kTCTableUpdateSectionActivity withNewObjects:activityItems fromOldObjects:previousActivityItems];
    }];
}


- (NSDictionary *) generateChangeSetsForSection:(NSString *) section withNewObjects:(NSOrderedSet *) newObjects fromOldObjects:(NSOrderedSet *) oldObjects {
    NSSet *newObjectsSet = [newObjects set];
    NSSet *previousObjectsSet = [oldObjects set];
    NSMutableSet *insertedObjects = [newObjectsSet mutableCopy];
    [insertedObjects minusSet:previousObjectsSet];
    NSMutableSet *deletedObjects = [previousObjectsSet mutableCopy];
    [deletedObjects minusSet:newObjectsSet];
    NSMutableSet *updatedObjects = [newObjectsSet mutableCopy];
    [updatedObjects minusSet:insertedObjects];
    [updatedObjects minusSet:deletedObjects];
    NSMutableSet *changes = [NSMutableSet set];
    for (id object in insertedObjects) {
        [changes addObject:@{kTCTableUpdateType: @(NSFetchedResultsChangeInsert),
                             kTCTableUpdateNewIndex: @([newObjects indexOfObject:object])}];
    }
    for (id object in deletedObjects) {
        [changes addObject:@{kTCTableUpdateType: @(NSFetchedResultsChangeDelete),
                             kTCTableUpdateOldIndex: @([oldObjects indexOfObject:object])}];
    }
    for (id object in updatedObjects) {
        [changes addObject:@{kTCTableUpdateType: @(NSFetchedResultsChangeMove),
                             kTCTableUpdateOldIndex: @([oldObjects indexOfObject:object]),
                             kTCTableUpdateNewIndex: @([newObjects indexOfObject:object])}];
    }
    return @{kTCTableUpdateSection: section,
             kTCTableUpdateChanges: [changes copy]};
}


// listening to the table update signal, perform the updates
    [self.viewModel.tableUpdateSignal
        subscribeNext:^(RACTuple *values) {
            @strongify(self);
            [self.tableView beginUpdates];
            for (NSDictionary *sectionChanges in values) {
                NSUInteger tableSection = [sectionChanges[kTCTableUpdateSection] isEqualToString:kTCTableUpdateSectionInbox] ? TableSectionInbox: TableSectionActivity;
                NSArray *changes = sectionChanges[kTCTableUpdateChanges];
                BOOL deletedEmptyStateRow = NO;
                BOOL insertedEmptyStateRow = NO;
                NSUInteger newCount = tableSection == TableSectionInbox ? self.viewModel.inboxItems.count : self.viewModel.activityItems.count;
                NSUInteger previousCount = tableSection == TableSectionInbox ? self.viewModel.previousInboxItems.count : self.viewModel.previousActivityItems.count;
                for (NSDictionary *change in changes) {
                    if (((NSNumber *)change[kTCTableUpdateType]).integerValue == NSFetchedResultsChangeInsert ) {
                        if (previousCount == 0 && !deletedEmptyStateRow) {
                            [self.tableView deleteRowsAtIndexPaths:@[[NSIndexPath indexPathForRow:0 inSection:tableSection]] withRowAnimation:UITableViewRowAnimationAutomatic];
                            deletedEmptyStateRow = YES;
                        }
                        [self.tableView insertRowsAtIndexPaths:@[[NSIndexPath indexPathForRow:((NSNumber *)change[kTCTableUpdateNewIndex]).integerValue inSection:tableSection]] withRowAnimation:UITableViewRowAnimationAutomatic];
                    } else if (((NSNumber *)change[kTCTableUpdateType]).integerValue == NSFetchedResultsChangeMove) {
                        [self.tableView moveRowAtIndexPath:[NSIndexPath indexPathForRow:((NSNumber *)change[kTCTableUpdateOldIndex]).integerValue inSection:tableSection]
                                               toIndexPath:[NSIndexPath indexPathForRow:((NSNumber *)change[kTCTableUpdateNewIndex]).integerValue inSection:tableSection]];
                    } else {
                        [self.tableView deleteRowsAtIndexPaths:@[[NSIndexPath indexPathForRow:((NSNumber *)change[kTCTableUpdateOldIndex]).integerValue inSection:tableSection]]
                                              withRowAnimation:UITableViewRowAnimationAutomatic];
                        if (newCount == 0 && !insertedEmptyStateRow) {
                            [self.tableView insertRowsAtIndexPaths:@[[NSIndexPath indexPathForRow:0 inSection:tableSection]] withRowAnimation:UITableViewRowAnimationAutomatic];
                            insertedEmptyStateRow = YES;
                        }

                    }
                }
            }
            [self.tableView endUpdates];
        }];