accessing images in nsmutablearray xcode

Question

I am converting individual images into UIImagePNGRepresentation but I keep getting a thread breakpoin ate let data = UIImagePNGRepresentation(tile as! UIImage)! ImageNameList is an nsmutablearray of images

var imageNameList: [String] {
    var imageNameList2:[String] = [] //[NSMutableArray]()
    for i in 0...149 {
        let imageName = String(format: "pic_%03d", Int(i))
        imageNameList2.append(imageName)
    }
    return imageNameList2
}

let table = PFObject(className: "Cool")
        let tilesPF = imageNameList.map({ tile in
            let data = UIImagePNGRepresentation(tile)! //cannot convert type string to type uiimage
            let file = PFFile(data: data)

            let tile = PFObject(className: "RealCool")
            tile["tile"] = file
        })

Answer 1

UIImage is not a subclass of PFObject, so the cast tile as! UIImage can never be successful. The Swift compiler should already be giving you a warning: “Cast from 'PFObject' to unrelated type 'UIImage' always fails”.