So my code was working perfectly fine but today it is returning nil when I try to cast Firebase's snapshot.value to a Bool. I haven't made any change to code at all. But it works fine if I cast it to a String (as? String returns "true").
Same issue at another place where I was casting to [String: Bool].
One thing that is different from earlier, I installed Xcode 10 beta 3 today (Xcode 9.4 is installed too). Both Xcode versions are returning nil. Here's the code:
if let currentUserId = Auth.auth().currentUser?.uid{
Database.database().reference().child("users/\(currentUserId)/share").observe(.childAdded) { (snapshot) in
let data = snapshot.value as? Bool
if data == true{
self.showNotificationsBadge()
}
}
}
Edit: Snapshot is not nil. You can see that in the console pane. I have printed both snapshot.key and .value.
Edit 2: I'm sorry if my question caused any confusions. The main purpose of this question is to know the problem, is it Firebase SDK or Xcode. Because it was working perfectly till now. I know how I can tackle this and how can I convert a String to a Bool.
Edit 3: Thank you everyone for your answers. I'm sorry I was unable to deliver my thoughts correctly. I just want to know about this unpredicted behavior and why is it happening? Who is the culprit here? Xcode, Firebase SDK? This code worked PERFECTLY FINE for about a month. I'm not asking for a solution, I'm just curious about this behavior. It would be great if someone from team Firebase can explain this issue.
Edit 4: Removed image and added code. Also figured out the issue thanks to #Jay's comment.
You need check if the snapshot is nil before checking the value.
if let data = snapshot.value as? Bool {
....
}
This happened to me just recently. I discovered that I had quotes around the child value, eg. "true". Remove the quotes and the solution from #Maximo should work as expected.
Related
I tried googling this problem but it seems like everyone has the opposite problem where the app runs on simulator but not their device. I've been struggling a LOT all week with firebase asynchronous calls returning null and linked the issue to persistence being enabled. All my problems go away if I disable persistence, but I want it enabled. I learned recently about synchronous issues with the different listeners/persistence and have been struggling with firebase returning outdated/nil values for a while.
Simulator was working just a week or two ago and I'm not sure what's changed. I've tried messing with / switching out .observeSingleEvent for .observe and still crashes at this code:
let synced = ref.child("profiles").child((FIRAuth.auth()?.currentUser?.uid)!).child("level")
synced.observeSingleEvent(of: FIRDataEventType.value, with: { (snapshot) in
print(snapshot)
print(snapshot.ref)
if (snapshot.value as! String == "One") {
........//CRASH
With the message:
Could not cast value of type 'NSNull' (0x10b7cf8c8) to 'NSString' (0x10a9dfc40).
When I try to print snapshot, it shows me an empty snapshot. But when I print the ref, the link works and takes me to the right place in my db (where I can see the data exists)
Any ideas how to fix/get around this without disabling persistence? Or more importantly I guess, should I care that it doesn't work in simulator if it works on a device? Will this matter for app store approval / affect future users?
If you'd like to see for yourself that this is an issue of firebase getting a nil/outdated value when the reference exists, here is what I see when I follow the printed ref link
The error seems fairly explicit: there is no value, so you can't convert it to a string.
synced.observeSingleEvent(of: FIRDataEventType.value, with: { (snapshot) in
if (snapshot.exists()) {
if (snapshot.value as! String == "One") {
........//CRASH
I'm not sure how to use the new UserDefaults class with the new Swift3 changes.
I had this code prior to the migration to swift3 which successfully retrieved the data stored in the userDefaults:
if NSUserDefaults.standardUserDefaults().objectForKey("profileArray") != nil {
profileArray = NSUserDefaults.standardUserDefaults().objectForKey("profileArray") as! [String]
}
With the migration to swift3 the code is now:
if UserDefaults.standard.object(forKey: "profileArray") != nil {
profileArray = UserDefaults.standard.object(forKey: "profileArray")! as! [NSString]
}
The new syntax makes sense but when I run the project the data that was previously stored in the user default seems to be gone.The userdefault.standard... is now returning empty/nil.
How do I retrieve the data that was stored prior to the swift3 migration?
Appreciate the help with moving to swift3!
I don't know if that solves your problem, but your syntax is not very efficient – you retrieve the object from user defaults unnecessarily twice.
The recommended way is optional binding and the dedicated method to get an array:
if let array = UserDefaults.standard.array(forKey: "profileArray") as? [String] {
profileArray = array
}
Im Swift use always String rather than NSString unless you have no choice.
I have finally figured this out. The userDefaults weren't "cleared". but the userDefaults are specific to a device. so with the migration to xcode8 the iOS simulators were also upgraded....and these are technically new devices where userDefaults had never been captured.
I proved this theory by adding a simulator (you can go back and re-install iOS 9.x simulators) and this worked.
I also tested on a real device using iOS 9.x & the new swift 3 code and the defaults persisted on that device.
So problem solved! :)
I came back to work on a project I have not touched in a week and suddenly my code was not working. I take a snapshot of data that I am sure exists (I can see it exactly in the database and changed no code) yet it is returning NSNULL for the snapshot and when I print snapshot.exists() I get false. I even tried printing snapshot.ref and typing that link into my browser and that takes me to the data on the console.
The only thing I did today was manually add a piece of data into my firebase console, but it was not in the same node where I am getting this error and it was working for a while after I made the change so I don't see how that could have caused this. Is anyone else having this issue or know why this would suddenly start happening?
Here is my code:
_ = ref.child("profiles").child((FIRAuth.auth()?.currentUser?.uid)!).child("type").observeSingleEventOfType(FIRDataEventType.Value, withBlock: { (snapshot) in
print(snapshot.exists())
print(snapshot.ref)
if (snapshot.value as! String == "Player") {
.....
}
})
I'm getting the error Could not cast value of type 'NSNull' (0x10d008600) to 'NSString' (0x10d3ffb48).' and as I said earlier snapshot.exists() is false and the ref link works.
Thanks!
I have created an iOS app using Swift and everything is working fine and dandy on the simulator. I get no errors or crashes at all, but when I submit my app to put up on the app store Apple rejects it and lets me know that it crashes when the user makes a selection. I cannot recreate this error/crash. I took the crash logs and symbolicated them. This line of code came up as the culprit for the crashes:
linksToPass = getLinks(season) as [String:[String]]
This line is trying to store the resulting Dictionary from the getLinks() function I created. It for sure is getting a dictionary and if there is no dictionary to send back I create a dictionary which has error information in it, so it is for sure returning a dictionary in that format no matter what. Seeing as I cannot recreate the crash, I am just trying to error check this line of code in any way possible so it does't crash when I resubmit to Apple.
I tried checking if the resulting dictionary was nil like so:
if(getLinks(seasons) != nil){
linksToPass = getLinks(season) as [String:[String]]
}
This is not valid though, and XCode lets me know that UInt8 is not compatible with NSDictionary or something of that nature.
I then fixed that line and changed it to this:
if(getLinks(seasons) != ["":[""]]){
linksToPass = getLinks(season) as [String:[String]]
}
I am just not sure if this is even a good way to check for errors. I was wondering if there were any suggestions on how I may go about making sure this line does not fail and result in a crash. Thank you very much.
EDIT:
Here is my getLinks() function if that helps add more info to the problem:
var season = ""
let hymn_links = Hymn_Links()
func getLinks (nameofseason:String) -> NSDictionary
{
switch (nameofseason)
{
default:
return ["Maps Not Found": []]
}
}
EDIT #2:
This is my updated getLinks() function with the use of optionals.
func getLinks (nameofseason:String) -> NSDictionary?
{
switch (nameofseason)
{
default:
return nil
}
}
Also in my statement of linksToPass I changed it to:
if let links = getLinks(season) as? [String:[String]]
{
linksToPass = links
hymnnames = [String] (linksToPass.keys)
}
There are some known issues with the Swift optimiser. Some people have resorted to shipping with debug builds.
My suggestion would be to test with an optimised build to see if you can reproduce it. You can then try shipping a debug build to the App store.
General Code Comments
Why are you returning an NSDictionary rather than a Swift dictionary anyway? Without knowing the contents and creation method for your hymn_links object I can't be sure how good it is.
I would avoid as casts until Swift 1.2 and stick to using as? and then handling the nil case. At least in your "Edit 2" a nil will cause a crash as nil cannot be cast to [String:[String]] although [String:[String]]? should be possible.
Can you guarantee that all of the items returned by the switch statement will never under any circumstances be nil? If not getLinks should return an Optional.
Note that is is virtually impossible for getLinks to know that one of the items will never be nil and in Swift un-handed nils are a crash waiting to happen. Unless all these methods correctly handle nil.
Return an Optional and handle that in the statement that calls getLinks.
Languages handle nils differently, Objective-C handles them rather well, Java and Swift by crashing. But Swift has a mechanism to handle nils without crashing: Optionals, use it.
I'm trying to read the Linkedin response in swift.
My object is something like this ["positions":["values":["data1","data2","data3"]]]
if let positions: NSDictionary = info["positions"] as NSDictionary!{
if let positionsInfo: [NSDictionary] = positions["values"] as? [NSDictionary]{
for position : NSDictionary! in positionsInfo {
dosomething(position, person:usr)
}
}
}
If I do a StepOver line by line it works correctly. But if I run it i'll get a EXC_BAD_ADDRESS(code=1,address=0x7966b04) I enabled Zombie objects and ran it on Instruments. I'm pretty sure this is the code which is causing the problem. But not sure what is wrong with it.
The moment you used ! you opened yourself up for crashes if there were any problem. You must use as? to make sure that the data is actually what you think it is.
There are many blog posts out there on how to safely parse JSON into Swift data structures. It's now almost a rite of passage for Swift bloggers.
http://robots.thoughtbot.com/efficient-json-in-swift-with-functional-concepts-and-generics
http://chris.eidhof.nl/posts/json-parsing-in-swift.html
https://github.com/owensd/json-swift
https://github.com/lingoer/SwiftyJSON
Of course the many packages: https://github.com/search?q=%5Bswift%5D+json
http://robnapier.net/functional-wish-fulfillment - My own version on top of all the others