Get value return of apollo.fetch in Swift IOS (Apollo Client)

Question

I've on my app Apollo client to make request GraphQL to an API. I want put my requests in a class like that:

 class requestAPI {
  static func checkUsername(nameUser: String!) -> Bool{
    var res: Bool = false
    Network.shared.apollo.fetch(query: CheckUsernameQuery(username: nameUser)) { result in
      switch result {
        case .success(let response):
          res = response.data?.checkUsername
          print(“Reponse: \(response.data?.checkUsername)“)
        case .failure(let error):
          print(“Error: \(error)“)
      }
    }
    return res
  }
}

So i just want to get value response.data.checkUsername and return it, but res is always false because i think that the fetch is asynch. So what can i do to get the value of response.data.checkUsername (it's a Bool) and return it ?

Thanks all

Answer 1

Cross-posting from the Apollo Spectrum Chat:

Hi! You'll need to use a completion closure like this:

static func checkUsername(nameUser: String!, completion: @escaping (Bool) -> Void) {
  Network.shared.apollo.fetch(query: CheckUsernameQuery(username: nameUser)) { result in
    switch result {
    case .success(let response):
      res = response.data?.checkUsername ?? false
      completion(res)
    case .failure(let error):
      // whatever error handling you want to do
  }
}

The closure is a function that you pass as a parameter, and then you call it with the result asynchronously rather than returning the result directly from the function.

This is a pretty common pattern in Swift - I'd recommend reading up on it. The Swift doc on closures is exceptionally long and probably a little too detailed as a starting point, but it covers a ton of stuff. I think a better intro-level piece is John Sundell's article about closures.