Как использовать dispatch_async в Swift 3?

Question

[Aleksandr Govorukhin]

Здравствуйте!
Пытаюсь парсить текст по api в вк, но с возвратом текста есть небольшие неполадки, в интернете почитал что нужно использовать что-то там асинхронно и объясняют языком не совсем понятным мне для реализации)) Может кто подсказать как вернуть text?

func getJSON(rs: String, tx: String) -> String {
        
        var text = ""
        
        let inputURL = self.inputURL.text
        
        let link = inputURL?.components(separatedBy: "wall")
        
        let baseURL = "https://api.vk.com/method/wall.getById?posts=\(link![1])&access_token=87c166c356c35f6d835048af60d84014fa57d4eae&v=5.64"
        
        let url = NSURL(string: baseURL)
        let request = NSURLRequest(url: url! as URL)
        let session = URLSession(configuration: .default)
        let task = session.dataTask(with: request as URLRequest) { (data, response, error) -> Void in
            
            if error == nil {
                
                let swiftyJSON = JSON(data: data!)
                let response = swiftyJSON[rs].arrayValue
                
                for tobject in response {
                    
                    let text = tobject[tx].stringValue
                }

            }
        }
        task.resume()
        
        return text
    }

Answer 1

[Aleksandr Govorukhin]

func parse(callback: @escaping (_ text: String, _ images: [String]) -> Void) {
        
        let baseURL = "https://api.vk.com/method/wall.getById?posts=-34451036_490279)&access_token=5502c502caef0d55e1758dd&v=5.64"
        
        let url = NSURL(string: baseURL)
        let request = NSURLRequest(url: url! as URL)
        let session = URLSession(configuration: .default)
        let task = session.dataTask(with: request as URLRequest) { (data, response, error) -> Void in
            
            if error == nil {
                
                let swiftyJSON = JSON(data: data!)
                let response = swiftyJSON["response"].arrayValue
                var links = [String]()
                
                for tobject in response {
                    
                    let text = tobject["text"].stringValue
                    let attachments = tobject["attachments"].arrayValue
                    
                    for photo in attachments {
                        
                        let searchPhoto = photo["photo"].dictionary
                        
                        if let val = searchPhoto?["photo_130"]?.stringValue {
                            
                            links.append(val)
                        }
                    }
                    
                    callback(text, links)
                }
            }
        }
        task.resume()
    }


 parse(callback: { (text, links) in
            recipe.descriptionRecipe = text
            (UIApplication.shared.delegate as! AppDelegate).saveContext()
            self.goToHome()

        })

Answer 2

[Антон Горб]

func getJSON(rs: String, tx: String, completion: @escaping ((String) -> Void)) {
        DispatchQueue.main.async { [weak self] in
            guard let `self` = self else { return }
            
            let inputURL = self.inputURL.text
            let link = inputURL?.components(separatedBy: "wall")
            let baseURL = "https://api.vk.com/method/wall.getById?posts=\(link![1])&access_token=87c166c356c35f6d835048af60d84014fa57d4eae&v=5.64"
            
            let url = URL(string: baseURL)
            let request = NSURLRequest(url: url! as URL)
            let session = URLSession(configuration: .default)
            
            session.dataTask(with: request as URLRequest) { (data, response, error) -> Void in
                if error == nil {
                    let swiftyJSON = JSON(data: data!)
                    let response = swiftyJSON[rs].arrayValue
                    for tobject in response {
                        completion(tobject[tx].stringValue)
                    }
                }
            }
        }
    }