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swiftsemaphorecompletion

Swift5. How to wait the request from another .swift file?

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There are 2 files:

1st - Network requests

2nd - ViewController, place where the result of getCities() -> Array<String> { ... } should be called (at leasted could be checked with print

Using this to make a request:

request.httpMethod = "GET"
request.allHTTPHeaderFields = headers
request.httpBody = postData as Data

    let session = URLSession.shared
    let dataTask = session.dataTask(with: request as URLRequest, completionHandler: { (data, response, error) -> Void in
      if (error != nil) {
        print(error as Any)
      } else { ...
}

The problem: The result of the request couldn't be accessed by UIViewController until the finish of the request. The list of UIViewController is initiated too early.

P.S: Already tried

semaphore

and

group

but as for me, it works only for the same class/file.

Solution

  • Don't ask, tell

    Use a completion handler to notify when the data are available. No semaphore, no group.

    func getCities(completion: @escaping ([String]) -> Void) { ... }

    and

    getCities { [weak self] cities in
    self?.list = cities
    print(cities)
    // do other stuff with received cities
}