I am trying to populate an array with a query from my parse database. When I try to print out the content of the array, I get an EXC_BAD_INSTRUCTION error. It doesn't seem like I'm properly appending new elements into my array, I'd appreciate any sort of tips
func loadSampleTasks() {
tasks = [Task]()
let query = PFQuery(className: "Task")
query.whereKey("TaskName", equalTo: "kenny")
query.findObjectsInBackgroundWithBlock() {
(objects: [PFObject]?, error: NSError?) -> Void in
if error == nil && objects != nil {
self.parseResults(objects!)
print(self.tasks) // this prints out Kenny object as expected
}
}
print(tasks) // prints an empty array
}
func parseResults(objects: Array<PFObject>){
for object in objects { //looping through returned data
print("no error in Parse lookup")
let parseResult1 = Task(name: object["TaskName"] as! String)
parseResult1?.completed = object["Completed"] as! Bool
print("Parse result in object loop: \(parseResult1!.name)")
tasks.append(parseResult1!)
}
}
Any help much appreciated!
To what thefredelement said, "This is happening because you're getting your parse results in a closure, which means it may execute after the function itself has already returned." Before this happens, though, it won't work properly and you'll come back with that error.
I got it to work. I had to tableView.reloadData() within the closure. Thank you so much for the help!
Related
Trying to get my question answered (Retrieve Boolean array from Firebase) I am trying to solve the question by myself. I think I am almost done but 1 thing is bugging me. I want to retrieve a boolean array and store it in a boolean array in my app.
This is what I got:
if snapshot.key == "whatAchievementsunlocked"
{
whatAchievementsUnlocked.removeAll()
if let snapshots = snapshot.children.allObjects as? [FIRDataSnapshot] {
for x in snapshots
{
print(x.value!) //prints 0
var valueForIndexX = x.value as! Int //crash
print(valueForIndexX)
if valueForIndexX == 0
{
whatAchievementsUnlocked.append(false)
}
else
{
whatAchievementsUnlocked.append(true)
}
}
}
}
Why would it crash there? If I use as?, the output would be nil. I also tried to use var valueForIndexX = Int(x.value!) But that gives me an error: Cannot invoke initializer for type Int with an argument list of type (Any). The output of x.value! is clearly an Int, why would this result in an error? The debug just shows "(lldb)". What am I doing wrong?\
When I try to store arrays from Parse into a local array I can only access it within the findObjectsInBackgroundWithBlock {...}. When I print it outside of that block, it shows []...
Code :
var qArray : [[Int]] = []
override func viewDidLoad() {
super.viewDidLoad()
let query = PFQuery(className: "Trivia")
query.findObjectsInBackgroundWithBlock {
(objects: [PFObject]?, error: NSError?) in
if objects != nil {
if let objects = objects {
for object in objects {
self.qArray.append(object["mainPattern"] as! [Int])
}
print(self.qArray) // Prints a multi dimension array
}
}
if error != nil {
print(error)
}
}
print(self.qArray) // prints []
}
It's most likely because the array hasn't been populated yet because it's running in the background. You can try using dispatch_group to circumvent this issue.
I think you're misunderstanding what findInBackground means. It means the code after the callback continues to execute, so it calls query.findInBackground.... and then it continues with the next line, which is print(self.qArray). At some point later on, it hears back from the database and it executes all the code inside the Callback, which is when the array finally gets populated.
I'm trying to retrive usernames from Parse's Server with findObjectsInBackgroundWithBlock. I want the results to be stored inside a NSArray, but I get an error in the code.
Here's it:
let query: PFQuery = PFUser.query()!
query.orderByAscending("username")
query.whereKey("username", notEqualTo: myUserId as! String)
query.findObjectsInBackgroundWithBlock {(objects:NSArray?, error:NSError?) -> Void in
}
And I'm getting this error:
Cannot convert value of type '(NSArray?, NSError?) -> Void' to expected argument type 'PFQueryArrayResultBlock?'
I know that everything is working when changing 'NSArray?' to '[PFObject]?', but I want to result to be an Array.. How can I solve this?
You need to do the following:
declare this:
var array:NSArray = NSArray()
query.findObjectsInBackgroundWithBlock {(objects:PFObject?, error:NSError?) -> Void in
if error != nil {
print("error")
} else {
if let objects = objects{
for object in objects {
self.append(object)
}
}
}
}
You can't force the conversion in the callback parameters. Your callback needs to respect the type that will be supplied and then your code in the callback can mutate the supplied parameters and store them.
I am receiving this strange error every time I process an address book ( using APAddressBOOK via cocapods) in Swift and after some debugging I found out that and empty object (record with no phone number) within the array causes this issue but am not sure how to get rid of it.
Here is my code:
func getPersonsNo(contactno: AnyObject) -> String {
println(contactno) // **when the object is empty I get this "[]"**
if let numberRaw = contactno.phones?[0] as? String { // at this statement the program crashes with a fatal error
println(numberRaw)
return numberRaw)
}
return " "
}
Any clues what is happening here?
The subscript of an Array doesn't return an optional to indicate if an index is out of range of the array; instead your program will crash with the message “fatal error: Array index out of range”. Applying this your code: when contactno is empty your program will crash because there's no element at index 0 of the array.
To easiest way to solve your problem is probably to use the first property on Array. first will return the first element in the array, or nil if the array is empty. Taking a look at how first is declared:
extension Array {
var first: T? { get }
}
As of Swift 2, first has been made an extension of the CollectionType protocol:
extension CollectionType {
var first: Self.Generator.Element? { get }
}
You'd use this like so:
if let numberRaw = contactno.phones?.first as? String {
// ...
}
I want the user to upload an image, and other users leave replies to that image. Everything works fine so far except if the row for that specific image object is empty, the app crashes.
fatal error: unexpectedly found nil while unwrapping an Optional value
Here is my code :
override func viewDidLoad() {
super.viewDidLoad()
var error = ""
var query = PFQuery(className:"Posts")
query.getObjectInBackgroundWithId(cellID) {
(objects: PFObject!, error: NSError!) -> Void in
if error == nil {
var array = objects.objectForKey("replies") as [String] // <- when error occurs the compiler point here.
for object in array {
self.repliesArray.append(object as String)
}
} else {
self.displayError("Error", error: "Error retreiving")
}
self.tableView.reloadData()
}
}
Does this work? You can't append null objects to an array so this appends an empty string instead of null. Also you need the explanation mark so that it can be nil.
var array = objects.objectForKey("replies") as [String!]
for object in array {
if object != nil {
self.repliesArray.append(object as String)
}
else {
self.repliesArray.append("")
}
}
query.getObjectInBackgroundWithId(cellID) {
(objects: PFObject!, error: NSError!) -> Void in
if error == nil {
var array = objects.objectForKey("replies") as [String] // <- when error occurs the compiler point here.
The key here is that you're accepting an implicitly unwrapped optional (PFObject!) which is implying a promise that it will never be nil, but is nil.
Ideally (*), the type should be (objects: PFObject?, error: NSError?) -> Void to make the optionals explicit and force you to do the nil checking that is required. I believe you can do this even if the caller claims to send you (PFObject!, NSError!) -> Void, since I think Swift will make the implicit->explicit conversion for you.
If that's still impossible, then you will have to manually verify that objects is not nil before using it. (This is unlike #Dehli's solution, which checks that the things contained in objects are non-nil. That's not the problem; the problem is that objects itself is nil.)
(*) I say "ideally" here in terms of the existing interface. Passing a tuple of optional value/error is a lousy pattern. The better solution is to use something like a Result object.