ios - 在 for 循环中完成 findObjectsInBackgroundWithBlock 后执行操作

Question

我的代码中有这样的结构:

for (METMeetingEntity *e in self.meetingList) {
            PFQuery *query = [PFUser query];        
            //some query constraints, depending on METMeetingEntity
            [query findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error)
            {
                // some query actions


                NSArray *sortDescriptors = @[[NSSortDescriptor sortDescriptorWithKey:@"date" ascending:YES]];
                self.meetingList = [NSMutableArray arrayWithArray:[self.meetingList sortedArrayUsingDescriptors:sortDescriptors]];
                self.meetingList = [self dateCleanup:self.meetingList];
            }];

我如何执行操作 - 在所有 findObjectsInBackground 完成后重新加载我的 TableView

Answer 1

一个可能的解决方案是保持计数。当数字与原始计数相符时，您就知道自己完成了。

NSUInteger count = self.meetingList.count;
for (METMeetingEntity *e in self.meetingList) {
    PFQuery *query = [PFUser query];        
    //some query constraints, depending on METMeetingEntity
    [query findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {
        // some query actions
        NSArray *sortDescriptors = @[[NSSortDescriptor sortDescriptorWithKey:@"date" ascending:YES]];
        self.meetingList = [NSMutableArray arrayWithArray:[self.meetingList sortedArrayUsingDescriptors:sortDescriptors]];
        self.meetingList = [self dateCleanup:self.meetingList];

        count--;
        if (count == 0) {
            dispatch_async(dispatch_get_main_queue(), ^{
                // reload table or whatever needs to be done
            });
        }
    }];
}