ios - Alamofire doesn't execute whole code in response closure

Question

I'm trying to get photos of user. On the TableView of friends list I call the function

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        guard segue.identifier == "showFriendSegue" else {return}
        guard let showFriend = segue.destination as? FriendCollectionViewController else {return}
        let indexPath = self.tableView.indexPathForSelectedRow
        let userKey = usersSectionTitles[indexPath!.section]
        if let userValues = usersDictionary[userKey] {
            let user = userValues[indexPath!.row]
            let id  = userValues[indexPath!.row].id
            showFriend.friend.append(user)
            showFriend.friendImages = Photo.photo.getUserPhotos(id: id)
        }
    }

func getUserPhotos(id: Int) -> [String]{
        let url = URL(string: "https://api.vk.com/method/photos.get")!
        let parameters: Parameters = [
            "owner_id" : id,
            "album_id" : "profile",
            "rev" : 1,
            "access_token" : Session.session.token,
            "v": Session.session.APIVersion
        ]
        
        var userPhotos: [String] = []
    
        AF.request(url, method: .get, parameters: parameters, headers: nil).responseJSON { (response) in
            switch response.result {
            case .success(let value):
                let json = JSON(value)
              
                let photosArray = json["response"]["items"].arrayValue

                for sizes in photosArray {
                    let onlyOneType = sizes["sizes"].arrayValue.filter({$0["type"] == "z"})
                    for url in onlyOneType {
                        userPhotos.append(url["url"].stringValue)
                    }
                }

            case .failure(let error):
                print(error)
            }
        }
        return userPhotos
    }

It seems for me like Alamofire doesn't have enough time to make whole code and it's strange because I expect that code should be executed consistently. When I check code with breakpoints I see that AF.request starts, then right away return userPhotos executes, photosArray is not empty but on the friend's page I have an empty array of photos. How should I fill the array from AF? I thought it was obvious and simple thing but I can't understand what's wrong with this closure.

标签： iosswift

Answer 1

Alamofire request runs asynchronously, that's why your code returns empty userPhotos at once. You need to use completion handler for this function. It will be called when your request returns a response with ids.

And I recommend to call this function in the FriendCollectionViewController instead of func prepare(for segue: UIStoryboardSegue, sender: Any?).

Attach code snippet below how to use completion for your case.

func getUserPhotos(id: Int, completion: @escaping (Result<[String], Error>) -> Void) {
        let url = URL(string: "https://api.vk.com/method/photos.get")!
        let parameters: Parameters = [
            "owner_id" : id,
            "album_id" : "profile",
            "rev" : 1,
            "access_token" : Session.session.token,
            "v": Session.session.APIVersion
        ]
        AF.request(url, method: .get, parameters: parameters, headers: nil).responseJSON { (response) in
            switch response.result {
            case .success(let value):
                let json = JSON(value)
              
                let photosArray = json["response"]["items"].arrayValue
                var userPhotos: [String] = []
                for sizes in photosArray {
                    let onlyOneType = sizes["sizes"].arrayValue.filter({$0["type"] == "z"})
                    for url in onlyOneType {
                        userPhotos.append(url["url"].stringValue)
                    }
                }
                completion(.success(userPhotos))

            case .failure(let error):
                print(error)
                completion(.failure(error))
            }
        }
    }

Then you can call your method.

Photo.photo.getUserPhotos(id: friend[0].id, completion: { result in
    switch result {
    case .success(let ids):
      // handle your ids here
    case .failure:(let error):
      // handle error
    }
})