PFObject not being casted into Subclass - ios

Question

*subclasses are registered in my app delegate
Users can create classroom objects. The problem is when a new classroom object is created, a following query will read the newest classroom as a PFObject. This will crash the program.
Previously made classrooms will be correctly read.
Also - when I close the app and restart it, the newest classroom is properly read as a classroom. How can I cast the newly created classroom into the right subclass?
The error received is:
fatal error: NSArray element failed to match the Swift Array Element type
Thanks!
Class code for classroom object:
class Classroom: PFObject, PFSubclassing{
var professorLastName: String?
var classTitle: String?
var toSchool: School?
var subjectLevel: String?
var subject: String?
var enrolledUsers: [PFUser]?
//THIS IS FOR CREATING A NEW CLASS
func enrollClass(){
let classroom = PFObject(className: "Classroom")
classroom["subject"] = self.subject
...
classroom.saveInBackgroundWithBlock { (success: Bool, error: NSError?) -> Void in
print("added student to class.")
}
}
//start protocol code for PFSubclass
static func parseClassName() -> String {
return "Classroom"
}
override class func initialize() {
var onceToken : dispatch_once_t = 0;
dispatch_once(&onceToken) {
self.registerSubclass()
}
}
//end
This is the QUERY that pulls classrooms from Parse database and puts it into table view row cells:
QUERY:
let query = PFQuery(className: "_User")
query.includeKey("enrolledClasses")
query.getObjectInBackgroundWithId(PFUser.currentUser()!.objectId!) {(result:PFObject?, error: NSError?) -> Void in
let userEnrolledClasses = result!["enrolledClasses"] as! [Classroom]
completionBlock(userEnrolledClasses)
Insertion into row cell:
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCellWithIdentifier("enrolledClassCell") as! EnrolledClassesTableViewCell
//THE CODE CRASHES HERE!!!!
let classroom = timelineComponent.content[indexPath.row] as? Classroom
//NSARRAY FAILED TO MATCH ARRAY TYPE -> It's still PFObject
classroom?.setClass()
cell.enrolledOption.text = classroom?.classTitle
return cell
}
Readout:
AppDelegate:
func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
Classroom.registerSubclass()
School.registerSubclass()
Post.registerSubclass()
PostPoints.registerSubclass()
ReplyPost.registerSubclass()
ReplyPostPoints.registerSubclass()
SubjectList.registerSubclass()
Parse.enableLocalDatastore()
**New code as per Daniel's fix...
So the objects are being read as classroom but now the attempt to pull data out of classroom objects is not work. So I want to set a label to be the classroom.classTitle for a table row, but the data is always nil...
//TIMELINE IMPLEMENTATION
func loadInRange(range: Range<Int>, completionBlock: ([Classroom]?) -> Void) {
Classroom.registerSubclass()
let query = PFQuery(className: "_User")
query.includeKey("enrolledClasses")
query.getObjectInBackgroundWithId(PFUser.currentUser()!.objectId!) {(result:PFObject?, error: NSError?) -> Void in
let rawPFObject = result!["enrolledClasses"] as! [PFObject]
var classroomArray: [Classroom] = []
for rawClassroom in rawPFObject{
let convertedClassroom = Classroom()
convertedClassroom.classTitle = rawClassroom["classTitle"] as? String
convertedClassroom.subject = rawClassroom["subject"] as? String
convertedClassroom.professorLastName = rawClassroom["professorLastName"] as? String
convertedClassroom.subjectLevel = rawClassroom["classTitle"] as? String
classroomArray.append(convertedClassroom)
}
completionBlock(classroomArray)
}
}
LABEL ASSIGNMENT:
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCellWithIdentifier("enrolledClassCell") as! EnrolledClassesTableViewCell
//the tableViewCell post is equal to the post[arrayNumber]
let classroom = timelineComponent.content[indexPath.row] as? Classroom
//CLASSROOM VALUES ARE ALL NIL HERE
classroom?.setClass()
cell.enrolledOption.text = classroom?.classTitle
return cell
}
Console readout:
Maybe it has to do with objectId being "new"?
Readout of timelineComponent.content

Answer 1

The problem you're having is that casting to an array of Classroom is not working correctly in your query. This may be a shortcoming of Parse object subclasses.
A workaround is to create a temporary array that will be passed to completionBlock.
In this temporary array will be added Classroom objects that are explicitly created as a Parse subclass.
In your Classroom class, add:
func loadFromObject(object: PFObject) {
// Setup a Classroom object from a PFObject.
self.subject = object["subject"]
...
}
In your query, replace these lines
let userEnrolledClasses = result!["enrolledClasses"] as! [Classroom]
completionBlock(userEnrolledClasses)
with
var classroomArray = Array<Classroom>()
for class in result!["enrolledClasses"] {
let newClass = Classroom().loadFromObject(class)
classroomArray.append(newClass)
}
completionBlock(classroomArray)