Swift: Unable to append struct instance to array - arrays

Question

I have been having some trouble creating a temporary array of user data from Firestore. Basically I created a function that retrieves user data from a Firestore collection and then iterates through each document within that collection, creating an instance of my "Thought" struct for each one. I then append each "Thought" instance to a temporary array called "tempThoughts", and the function then returns that array. The problem is that nothing seems to be appended to the array in the function. When I test it by printing out the contents of the array upon completion, it just prints an empty array.
The data itself is being read from the Firestore collection as it prints out each document the function iterates through, so I don't think that is the problem. I also tried checking to see if I am actually creating instances of the "Thought" struct properly by printing that out, and that seemed to be working. Does anyone have any idea what's wrong with the way I am appending the struct instances to the array? Perhaps there is a better way to go about doing this? Thanks for any help in advance.
Here is my current function:
func getUserDocuments() -> [Thought]{
var tempThoughts = [Thought]()
db.collection(cUser!.uid).getDocuments() { (querySnapshot, err) in
if let err = err {
print("Error getting documents: \(err)")
} else {
for document in querySnapshot!.documents {
print("\(document.documentID) => \(document.data())")
let tempThought: Thought = Thought(id: document.get("id") as! String, content: document.get("content") as! String, dateCreated: document.get("timestamp") as! String, isFavorite: (document.get("isFavorite") != nil))
tempThoughts.append(tempThought)
}
}
}
print("TEST")
print(tempThoughts)
return tempThoughts
}

Answer 1

Your getDocuments is an asynchronous operation. And you've updated your tempThoughts in it's completion only. But the place where you've printed it out will get executed before the getDocuments completion. Check out the order of results logged in the console.

Answer 2

You need to update your code like this
func getUserDocuments(_ onSuccess: ((_ thoughts: [Thought] ) -> Void), onFailuer: ((_ error: String) -> Void)) {
var tempThoughts = [Thought]()
db.collection(cUser!.uid).getDocuments() { (querySnapshot, err) in
if let err = err {
print("Error getting documents: \(err)")
onFailuer(err)
} else {
DispatchQueue.main.async {
for document in querySnapshot!.documents {
print("\(document.documentID) => \(document.data())")
let tempThought: Thought = Thought(id: document.get("id") as! String, content: document.get("content") as! String, dateCreated: document.get("timestamp") as! String, isFavorite: (document.get("isFavorite") != nil))
tempThoughts.append(tempThought)
}
print("TEST")
print(tempThoughts)
onSuccess(tempThoughts)
}
}
}
}
user this code
And you can use this function like this
getUserDocuments({ (thoughts) in
// Your logic
}) { (error) in
// error Occured
}