如何使用ObjectIds的解析数组填充UICollectionView？

Question

I am using Parse.com. I have an array(named "Wants" of objectIds that I want to use to populate a UICollectionView with each objectId's corresponding image. I'm not quite sure where to start.

I tried using a PFQuery with a Wherekey of "Wants", but I'm not sure what to put in the "equalTo" parameter.

        var downloadCards = PFQuery(className: "User")
        downloadCards.whereKey("Wants", equalTo:"")
        downloadCards.orderByAscending("Number")
        downloadCards.limit = 200
        downloadCards.findObjectsInBackgroundWithBlock {

            (objects: [AnyObject]?, error: NSError?) -> Void in
            if error == nil {
                if let objects = objects as? [PFObject] {
                    for object in objects {
                        objectIds.append(object.objectId!)
                        parseObjects.append(object["Image"] as! PFFile)
                        imageNames.append(object["Number"] as! String)
                        imageExpansions.append(object["ExpansionNumber"] as! String)
                        self.collectionView.reloadData()
                    }
                }
            } else {
                println("Error: \(error!) \(error!.userInfo!)")
            }
        }

Collection View code here:

func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {

    return parseObjects.count

}

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

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

    parseObjects[indexPath.row].getDataInBackgroundWithBlock{

        (imageData: NSData?, error: NSError?) -> Void in

        if error == nil {

            let image = UIImage(data: imageData!)

            cell.cardsImg.image = image

        }   

    }
    return cell
}

Answer 1

Yes you can but the function

// Initialise the PFQueryTable tableview
override init!(style: UITableViewStyle, className: String!) {
    super.init(style: style, className: className)
}

required init(coder aDecoder: NSCoder) {
    super.init(coder: aDecoder)

    // Configure the PFQueryTableView
    self.parseClassName = "yourClass"

    self.textKey = "yourObject"
    self.pullToRefreshEnabled = true
    self.paginationEnabled = false
}

Is async so your collectionView function is returning an empty cell. The easiest way around is to download all the data and just than update your collection view

Answer 2

Instead of using whereKey(key:equal:To) use whereKeyExists(key). This will return all objects that have a Wants array.

downloadCards.whereKeyExists("Wants")