Firebase getIDToken and how to use it in an API call - swift

Question

I have an API call that grabs json, but requires token authentication. Token auth works great, but when I try and pass the token along to the API function, it's coming back nil. I believe it's because Auth.auth().currentUser!.getIDToken(...) hasn't actually completed yet. Relevant code below... How do I modify this to
class SessionData : ObservableObject {
...
func token() -> String? {
var result: String? = nil
Auth.auth().currentUser!.getIDToken(completion: { (res, err) in
if err != nil {
print("*** TOKEN() ERROR: \(err!)")
} else {
print("*** TOKEN() SUCCESS: \(err!)")
result = res!
}
})
return result
}
...
}
class FetchPosts: ObservableObject {
#Published var posts = [Post]()
func load(api: Bool, session: SessionData) {
if api {
let url = URL(string: MyAPI.getAddress(token: session.token()!))!
URLSession.shared.dataTask(with: url) {(data, response, error) in
do {
if let postsData = data {
// 3.
let decodedData = try JSONDecoder().decode(Response.self, from: postsData)
DispatchQueue.main.async {
self.posts = decodedData.result
if decodedData.error != nil {
print("ERROR: \(decodedData.error!)")
session.json_error(error: decodedData.error!)
}
}
} else {
print("No data. Connection error.")
DispatchQueue.main.async {
session.json_error(error: "Could not connect to server, please try again!")
}
}
} catch {
print("* Error: \(error)")
}
}.resume()
} else {
let url = Bundle.main.url(forResource: "test", withExtension: "json")!
let data = try! Data(contentsOf: url)
let decoder = JSONDecoder()
if let products = try? decoder.decode([Post].self, from: data) {
self.posts = products
}
}
}
}
And this is how the .load function is called:
UserViewer(fetch: posts)
.transition(AnyTransition.slide)
.animation(.default)
.onAppear {
withAnimation{
posts.load(api: true, session: session)
}
}
.environmentObject(session)

Answer 1

Because getIDToken executes and returns asynchronously, you can't return directly from it. Instead, you'll need to use a callback function.
Here's a modification of your function:
func token(_ completion: #escaping (String?) -> ()) {
guard let user = Auth.auth().currentUser else {
//handle error
return
}
user.getIDToken(completion: { (res, err) in
if err != nil {
print("*** TOKEN() ERROR: \(err!)")
//handle error
} else {
print("*** TOKEN() SUCCESS: \(err!)")
completion(res)
}
})
}
Then, you can use it later on:
.onAppear {
session.token { token in
guard let token = token else {
//handle nil
return
}
withAnimation{
posts.load(api: true, session: session, token: token)
}
}
}
Modify your load to take a token parameter:
func load(api: Bool, session: SessionData, token: String) {
if api {
guard let url = URL(string: MyAPI.getAddress(token: token)) else {
//handle bad URL
return
}
Also, as you can see I'm doing in my code samples, I would try to get out of the habit of using ! to force unwrap optionals. If the optional is nil and you use !, your program will crash. Instead, familiarize yourself with guard let and if let and learn to handle optionals in a way that won't lead to a crash -- it's one of the great benefits of Swift.