Get value from callback function swift - swift

Question

Question I want to get the value returned from my ApiToken function so I can use it in another function. For some reason I can not get the value from this function it will not return anything. How could I return the value from my ApiToken function and use it in another function.
Here is my GetApiToken class with the ApiToken function
class GetApiToken {
public func ApiToken(link: String, completionBlock: #escaping (String) -> Void) -> Void
{
let url = URL(string: link)!
let jsonDict = ["username": "snow", "password": "ssssssssss"]
let jsonData = try! JSONSerialization.data(withJSONObject: jsonDict, options: [])
var request = URLRequest(url: url)
request.httpMethod = "post"
request.setValue("application/json", forHTTPHeaderField: "Content-Type")
request.httpBody = jsonData
let task = URLSession.shared.dataTask(with: request) { (data, response, error) in
if let error = error {
print("error:", error)
return
}
do {
guard let data = data else { return }
guard let json = try JSONSerialization.jsonObject(with: data, options: []) as? [String: AnyObject] else { return }
//self.token = json["access_token"] as? String ?? "x"
completionBlock((json["access_token"] as? String)!)
} catch {
print("error:", error)
}
}
task.resume()
}
}
Here is where I am trying to get the value
func getData(_ link:String)
{
let url = URL(string: link)!
var request = URLRequest(url: url, cachePolicy: .reloadIgnoringCacheData, timeoutInterval: 20)
request.httpMethod = "GET"
var output = ""
GetApiToken().ApiToken(link: "http://localhost:5000/auth", completionBlock: { str in
output = str
})
request.addValue("JWT \(output)", forHTTPHeaderField: "Authorization")
request.setValue("application/json", forHTTPHeaderField: "Content-Type") ..........

Answer 1

It's an asynchronous call, so you need to put everything that will happen once the data has been retrieved in the completion callback
func getData(_ link:String)
{
let url = URL(string: link)!
var request = URLRequest(url: url,
cachePolicy: .reloadIgnoringCacheData,
timeoutInterval: 20)
request.httpMethod = "GET"
GetApiToken().ApiToken(link: "http://localhost:5000/auth",
completionBlock:
{ output in
request.addValue("JWT \(output)", forHTTPHeaderField: "Authorization")
request.setValue("application/json", forHTTPHeaderField: "Content-Type")
.......
})