Method to return value retrieved from HTTP request [duplicate] - swift

Question

This question already has answers here:
Returning data from async call in Swift function
(13 answers)
Closed 4 years ago.
I have a method which performs an HTTP request and retrieves data from a website, it's working as expected, I'm getting the data correctly. What I haven't been able to do is return the retrieved value when the method is called.
Here is the code...
func myFunction(zipCode: String)->String{
var myData:String = ""
let siteLink = "http://example.com/zip/" + zipCode
let url = URL(string: siteLink)
let task = URLSession.shared.dataTask(with: url!) { data, response, error in
guard error == nil else {
print(error!)
return
}
guard let data = data else {
print("Data is empty")
return
}
let json = try! JSONSerialization.jsonObject(with: data, options: [])
guard let jsonArray = json as? [[String: String]] else {
return
}
myData = jsonArray[0]["MyPropertyName"]!
// Here, myData outputs, "Info for zip code 52484 from HTTP request"
}
task.resume()
return myData
}
When I call myFunction I get and empty string...
myFunction(zipCode: "52484")// Outputs an empty string
What I was expecting to see is a return value of "Info for zip code 52484 from HTTP request" since the myData variable was modified inside the let task = before the return call. I tried returning inside the let task = but this cannot be done in Swift.
How can I return the retrieved value when the myFunction is called?

Answer 1

You need a completion as request is asynchronous
func myFunction(zipCode: String,completion:#escaping(_ str:String?) -> () ) {
let siteLink = "http://example.com/zip/" + zipCode
let url = URL(string: siteLink)
let task = URLSession.shared.dataTask(with: url!) { data, response, error in
guard error == nil else {
print(error!)
completion(nil)
return
}
guard let data = data else {
print("Data is empty")
completion(nil)
return
}
let json = try! JSONSerialization.jsonObject(with: data, options: [])
guard let jsonArray = json as? [[String: String]] else {
completion(nil)
return
}
let myData = jsonArray[0]["MyPropertyName"]!
completion(myData)
}
task.resume()
}
Call
myFunction(zipCode: "52484") { (str) in
if let st = str {
print(st)
}
}