如何从Firebase提取图像以在scrollView中显示

Question

var rewardDataArr：[URL] = [] func showImageRewardData（rewardID：String，ImageView：UIImageView）{

    let databaseRef = Database.database().reference().child("reward").child(rewardID).child("rewardImage")
    databaseRef.observe(DataEventType.value, with: { (Snapshot) in
        if Snapshot.childrenCount>0{

            for rewardImage in Snapshot.children.allObjects as! [DataSnapshot]{
                let rewardObject = rewardImage.value as? [String: AnyObject]

                if(rewardObject?["imageURL"] != nil){
                    let imageUrl = rewardObject?["imageURL"] as! String

                    rewardDataArr.append(NSURL(string: imageUrl)! as URL)