Synchronized code in iOS/Swift [duplicate] - ios

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How to return value from Alamofire
(5 answers)
Closed 5 years ago.
I am new with iOS programming. I am trying to make a piece of code in my function be synchronized, but it doesn't seem to work:
func fetchLocationsList(searchText:String)->Array<String> {
print ("searched text:\(searchText)")
let url = URL(string:"http://api.openweathermap.org/data/2.5/find?q=\(searchText)&type=like&sort=name&cnt=9&APPID=a33aa72")
//Using Alamofire to handle http requests
Alamofire.request(url!).responseJSON {response in
guard let jsonResponse = response.result.value as? [String:Any]
else { print ("error in json response")
return}
guard let list = jsonResponse["list"] as? NSArray else {return}
let lockQueue = DispatchQueue(label:"Et.My-Weather-App.queue1")
_ = lockQueue.sync{
for index in 0..<list.count {
print ("index is: \(index)")
guard let listElement = list[index] as? [String:Any] else {return}
let id = listElement["id"] as! Int
print ("id is: \(id)")
let cityName = listElement["name"] as! String
print ("cityName is: \(cityName)")
let sys = listElement["sys"] as! [String:Any]
let country = sys["country"] as! String
print ("country is: \(country)")
let element = "\(cityName), \(country), \(id)"
print ("\(element)")
self.resultsArray.append(element)
}
}
}
if self.resultsArray.count==0 {
print ("results array is also zero!")
}
return self.resultsArray
}
When I run it, I see that the line "results array is also zero!" is printed before the "for" loop fills the resultArray with elements, so the returned resultArray is always empty!
What am I doing wrong?

Answer 1

I suggest you do this as async tasks are a pain and this works quite well.
func fetchLocationsList(searchText:String, completion: #escaping (_ results:Array<String>)->()){
print ("searched text:\(searchText)")
let url = URL(string:"http://api.openweathermap.org/data/2.5/find?q=\(searchText)&type=like&sort=name&cnt=9&APPID=a33aa72")
//Using Alamofire to handle http requests
Alamofire.request(url!).responseJSON {response in
guard let jsonResponse = response.result.value as? [String:Any] else { print ("error in json response"); return}
guard let list = jsonResponse["list"] as? Array<Dictionary<String,Any>> else { return }
var array = Array<String>() // create an array to store results.
for item in list {
let id = item["id"] as! Int
let cityName = item["name"] as! String
let sys = item["sys"] as! Dictionary<String,Any>
let country = sys["country"] as! String
let element = "\(cityName), \(country), \(id)"
array.append(element) // add to that array.
}
completion(array) //send the array via the completions handler.
}
}
So in your viewDidLoad or whatever.
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
fetchLocationsList(searchText: "Whatever this string is") { (results) in
self.resultsArray.append(contentsOf: results)
// Then do anything else you need to do after this function has completed within this closure.
}
}