在Parse上从缓存UITableView数据加载

Question

我有一个嵌套查询，如下所示，即使我使用（或我认为我使用）解析缓存，加载过程也需要3-4秒。 它不符合我的预期。 是否有可能在首次启动时从缓存加载，然后从解析云进行更新。 我是否至少需要核心数据或sqlite3才能与本地端的解析同步？

另外，当我使用“ query.cachePolicy”表视图获取重复的结果时，如何以正确的方式使用它。

- (void) retrieveSnapsFromParse {

NSString *currentUserName = [PFUser currentUser].username;

PFQuery *retrieveSnaps = [PFQuery queryWithClassName:@"Snap"];
[retrieveSnaps whereKey:@"from" equalTo:[PFUser currentUser].username];

PFQuery *retrieveSnaps2 = [PFQuery queryWithClassName:@"Snap"];
[retrieveSnaps2 whereKey:@"to" equalTo:[PFUser currentUser].username];

PFQuery * query = [PFQuery orQueryWithSubqueries:@[retrieveSnaps, retrieveSnaps2]];
query.cachePolicy = kPFCachePolicyCacheThenNetwork;
[query orderByDescending:@"createdAt"];
[query findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {
    if (!error) {
    for (PFObject *object in objects) {

            Snap *snap = [Snap new];

     if([currentUserName isEqualToString:[object objectForKey:@"to"]]) {
                snap.userName = [object objectForKey:@"from"];
                snap.sentOrReceived = @"Received";

                PFFile *snapImageFile = [object objectForKey:@"snappedimage"];
                [snapImageFile getDataInBackgroundWithBlock:^(NSData *data, NSError *error) {
                    if (!error) {
                        UIImage *snapImage = [UIImage imageWithData:data];
                        snap.snapImage = snapImage;
                    }
                }];

            } else if([currentUserName isEqualToString:[object objectForKey:@"from"]]) {
                snap.userName = [object objectForKey:@"to"];
                snap.sentOrReceived = @"Sent";

            }


            snap.opened = [object[@"opened"]boolValue];
            snap.counter = [object[@"second"]intValue];
            snap.objectId = [NSString stringWithFormat:@"%@",object.objectId];

            NSDate *createdAt = object.createdAt;
            snap.createdDate = createdAt;

    // Profile image for UICustomTableViewCell
      PFQuery *userQuery = [PFUser query];
            [userQuery whereKey:@"username" equalTo:snap.userName];
             userQuery.cachePolicy = kPFCachePolicyCacheElseNetwork;
            [userQuery getFirstObjectInBackgroundWithBlock:^(PFObject *object, NSError *error) {
                if (object) {
                    snap.userFirstName = [object objectForKey:@"firstname"];
                    PFFile *imageFile = [object objectForKey:@"profileimage"];
                    [imageFile getDataInBackgroundWithBlock:^(NSData *data, NSError *error) {
                        if (!error) {
                            UIImage *image = [UIImage imageWithData:data];
                            snap.userProfileImage = image;

                        }

                    }];

                    [snapsTemp addObject:snap];
                }

        snapsTable = snapsTemp;
                    [self.tableView reloadData];

            }];
     }
    }
}];

}

我在下面的cellForRowAtIndexPath上使用的代码；

cell.cellUserProfileImage.image = snap.userProfileImage;

也在.m文件中用于可变数组

    @implementation SnapsVC
{
    NSMutableArray *snapsTable;
}

Answer 1

将下面的代码放入cellForRowAtIndexPath而不是restoreSnapsFromParse后，它开始按预期运行

PFQuery *userQuery = [PFUser query];
[userQuery whereKey:@"username" equalTo:snap.userName];
userQuery.cachePolicy = kPFCachePolicyCacheElseNetwork;
[userQuery getFirstObjectInBackgroundWithBlock:^(PFObject *object, NSError *error) {
    if (object) {

        PFFile *imageFile = [object objectForKey:@"profileimage"];
        [imageFile getDataInBackgroundWithBlock:^(NSData *data, NSError *error) {
            if (!error) {
                cell.cellUserProfileImage.image = [UIImage imageWithData:data];
            }

        }];

        cell.cellUserFirstNameLabel.text = [object objectForKey:@"firstname"];
    }
}];