Firebase storage error - ios

Question

FirebaseStorage Pod Version (1.0.1)
var storageRef: FIRStorageReference! = FIRStorage.storage().reference()
let uploadTask = storageRef.putData(UIImagePNGRepresentation(image)!, metadata: nil) { metadata, error in
if (error != nil) {
} else {
let downloadURL = metadata!.downloadURL
print(downloadURL)
}
}
I simply selected a image from ImagePicker and tried to save Image data to the firebase storage. As illustrated in firebase docs.(Docs Reference) Upload from data in memory section.
It's throwing following error:
*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[__NSPlaceholderDictionary initWithObjects:forKeys:count:]: attempt to insert nil object from objects[1]'
*** First throw call stack:
(
0 CoreFoundation 0x02025494 __exceptionPreprocess + 180
1 libobjc.A.dylib 0x03eb2e02 objc_exception_throw + 50
2 CoreFoundation 0x01f0c6d2 -[__NSPlaceholderDictionary initWithObjects:forKeys:count:] + 386
3 CoreFoundation 0x01f2095b +[NSDictionary dictionaryWithObjects:forKeys:count:] + 75
4 FirePlay 0x001e42bc -[FIRStorageUploadTask enqueue] + 815
5 FirePlay 0x001e010c -[FIRStorageReference putData:metadata:completion:] + 880
The same code used to work before. I am not sure what's the problem now.

Answer 1

Turns out that we can't put files in root storage node. need to create child node and then only you can save the file. It was clearly mentioned in the Firebase docs somehow I overlooked it.
E.g
let mountainsRef = storageRef.child("mountains.jpg")
let uploadTask = mountainsRef.putData(UIImagePNGRepresentation(image)!, metadata: nil) { metadata, error in
if (error != nil) {
} else {
let downloadURL = metadata!.downloadURL
print(downloadURL)
}
}