How to resolve Escaping closure captures 'inout' parameter 'data' - ios

Question

I have the following function in a separate swift file which I use to make Firebase calls for data:
func fetchPosts(data: inout [Post]) {
postRef.observe(DataEventType.value) { (snapshot) in
data.removeAll() // ***Error thrown here***
if snapshot.value is NSNull {
} else {
var counter: UInt = 0
for item in snapshot.children {
let userID = (item as! DataSnapshot).key
self.postRef.child(userID).observe(DataEventType.value) { (snap) in
counter = counter + 1
for child in snap.children {
if let snapshot = child as? DataSnapshot,
let post = Post(snapshot: snapshot) {
data.append(post) // ***Error thrown here***
}
if (counter == snapshot.childrenCount) {
data = data.sorted(by: { $0.id > $1.id }) // ***Error thrown here***
}
}
}
}
}
}
}
In my view I have the following:
#State var posts: [Post] = [] // which is the place holder for the posts data
and then i have the following call
func fetchPosts() {
postStore.fetchPosts(data: &posts)
}
Which calls the function above and passes the [Post] array by reference
My issue is that I get the following error Escaping closure captures 'inout' parameter 'data' in the above function and I can not figure out what I need to do to resolve it!?
Has anyone ever encountered this error and what do you do to resolve it!?

Answer 1

That won't work with #State, instead you have to use completion callback pattern, like
func fetchPosts() {
self.posts = [] // reset
postStore.fetchPosts() { newPosts in
DispatchQueue.main.async {
self.posts = newPosts
}
}
}
and fetching function
func fetchPosts(completion: #escaping ([Post]) -> () ) {
// ...
var data: [Post] = [] // data is a local variable
// ...
if (counter == snapshot.childrenCount) {
completion(data.sorted(by: { $0.id > $1.id }))
}
// ...
}