如何从解析中过滤数据并在collectionview中显示

Question

I'm trying to populate a collectionview with different data depending on a button that the user taps. When I run this though, it throws an error: "[PFObject whereKey:equalTo:]: unrecognized selector sent to instance". How can I filter this data and get it to show correctly? Thanks in advance!

func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {

      let cell: iconCollectionViewCell = collectionView.dequeueReusableCellWithReuseIdentifier("Cell", forIndexPath: indexPath) as! iconCollectionViewCell

      if button1.selected {

            let stance = stances[indexPath.row].whereKey("stanceType", equalTo: "Character")
            iconImage = (stance.valueForKey("iconUnselected") as? PFFile)!
            cell.emojiIconPFImageView.file = iconImage
            cell.emojiIconPFImageView.loadInBackground()

      } else if button2.selected {

         let stance = stances[indexPath.row].whereKey("stanceType", equalTo: "Policy")
         iconImage = (stance.valueForKey("iconUnselected") as? PFFile)!
         cell.iconPFImageView.file = iconImage
         cell.iconPFImageView.loadInBackground()
      }

Answer 1

You are close in setting up a query on Parse.

Here's an example adapted to your problem.

let query = PFQuery(className: "MyParseClass")
query.whereKey("stanceType", equalTo:"Character")
query.findObjectsInBackgroundWithBlock {
    (objects: [PFObject]?, error: NSError?) -> Void in

    if error == nil {
        // The find succeeded.
        print("Successfully retrieved \(objects!.count) objects.")
        // Do something with the found objects
        if let objects = objects {
            for object in objects {
                print(object.objectId)
            }
        }
    } else {
        // Log details of the failure
        print("Error: \(error!) \(error!.userInfo)")
    }
}

You can store the results of the query in an array that can be used by the data source of your collection view.

The query needs to complete before you show your collection view or else you won't have any data to display.