如何从 Parse.com 检索某些图像

Question

我通过填充“imageFilesArray”并告诉 UICollectionViewCells 使用其数据来加载登录用户在先前视图控制器中选择的特定图像的“房间”UICollectionView：

-(void) retrieveSelectedImagesForRooms
{
//parse query where we search the selectedImage array column and return any entry where the array contains the logged in user objectid

   PFQuery *getRooms = [PFQuery queryWithClassName:@"collectionViewData"];
   [getRooms whereKey:@"selectedImage" equalTo:[PFUser currentUser].objectId];

   [getRooms findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {
    if (!error)
    {
        imageFilesArray = [[NSArray alloc] initWithArray:objects];
        [roomsCollection reloadData];
    }
}];
}

下一页必须显示用户为之前选择的房间图像选择的特定灯光。 So I add the row's objectid I've just selected to a new column on Parse, called "clickedRoom", when the room is selected:

-(void)selectedRoom:(PFObject*)object
{
    [object addUniqueObject:object.objectId forKey:@"clickedRoom"]; //put object id into clickedRoom column on Parse to save what room you specifically chose so that the light images correspond to only that room

    [object saveInBackgroundWithBlock:^(BOOL succeeded, NSError *error)
    {
    if (!error){}
    else{}
}];
}


- (void)collectionView:(UICollectionView*)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath {

   [self selectedRoom:[imageFilesArray objectAtIndex:indexPath.row]];
   [self performSegueWithIdentifier:@"myLights" sender:self];

}

现在，在“灯光”页面中，我只需要在“clickedRoom”列中显示具有所选房间的 objectid 的灯光图像。我相信这与我检索房间图像的原理相同，但我无法弄清楚我应该查询什么，例如：

-(void) retrieveCorrespondingImagesForLights
{
   PFQuery *getLights = [PFQuery queryWithClassName:@"collectionViewData"];
   [getLights whereKey:@"clickedRoom" equalTo:**MY-PREVIOUSLY-SELECTED-ROW**.objectid];
   [getLights findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {
    if (!error)
    {
        imageFilesArray = [[NSArray alloc] initWithArray:objects];
        [myLightsCollection reloadData];
    }
}];

}

有什么建议吗？！

Answer 1

retrieveCorrespondingImagesForLights 与您的 roomsCollection 位于不同的视图控制器中，对吗？如果是这样，那么您需要将所选房间的对象 id 传递给新的视图控制器，该控制器在[self performSegueWithIdentifier:@"myLights" sender:self];

看这里Pass Index Number between UITableView List segue

在您的情况下，您应该向目标视图控制器（我将其称为 LightsViewController）添加一个属性来捕获对象，或者 objectId 如果这是您查询所需的全部内容。我会建议这样的事情：

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{   
  if ([segue.identifier isEqualToString:@"myLights"]) {

    // note that "sender" will be the cell that was selected
    UICollectionViewCell *cell = (UICollectionViewCell*)sender;
    NSIndexPath *indexPath = [roomsCollection indexPathForCell:cell];

    LightsViewController *vc = (LightsViewController*)[segue destinationViewController];
    vc.selectedObject = indexPath.row;
  }
}

然后，在retrieveCorrespondingImagesForLights：

PFQuery *getLights = [PFQuery queryWithClassName:@"collectionViewData"];
[getLights whereKey:@"clickedRoom" equalTo:self.selectedObject.objectid];

编辑*

在不了解您的具体实现细节的情况下，您似乎正在尝试使用 Parse 在您的视图控制器之间传递数据，而您更适合在您的应用程序中本地执行此操作。也许我误解了你的问题。