Use Callbacks in Swift in place of Delegates

Callbacks in Swift

when we need to call any request to the network we most probably use delegate methods to send data and get a response when you only need to call a single function we will create for them an interface (Protocol in swift) which is not a good programming practice. So if you need to call a single you must use the callbacks in swift if you need to implement more than one function and also want that these all functions are to be implemented in your class you can use delegates. Here is the steps to create the callback in swift:-

• Create class for calling your network request by name NetworkManager
  
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  import Foundation   class NetworkManager: NSObject {   }

• Create a function in class  NetworkManager to which you want to send your network request
  
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  func fetchData(params : String , _ completion: @escaping ServiceResponse) -> Void {      }

• ServiceResponse is a  typealias which will contain your response and error
  
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  typealias ServiceResponse = (JSON?, Error?) -> Void   //JSON it is Swifty json object you can use Any or AnyObject or NSdictionary or Dictionary in which format you need the data   // Error will if your request contains an error

• Write your code in function fetchData
  
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  func fetchData(params : String , _ completion: @escaping ServiceResponse) -> Void {             var baseURLWithAPIKeyString = "\(self.baseURLString)\(params)/"                     let requestURL: String = baseURLWithAPIKeyString             print(requestURL)             var request1 = URLRequest(url: URL(string : requestURL)!)             request1.httpMethod = "GET"             request1.cachePolicy = NSURLRequest.CachePolicy.reloadIgnoringCacheData              let encodedData = GlobalData.Credentials.BASEDATA.data(using: String.Encoding.utf8)!             let base64String = encodedData.base64EncodedString()             request1.addValue("application/json", forHTTPHeaderField: "Content-Type")             request1.addValue("application/json", forHTTPHeaderField: "Accept")             request1.setValue("Basic \(base64String)", forHTTPHeaderField: "Authorization")             Alamofire.request(request1).responseJSON { (response) in                 switch response.result {                 case .success:                     let jsonData  = JSON.init(data: response.data!)                     completion(jsonData  , nil)                   case .failure(let error):                     completion( nil  ,  error as NSError)                 }          }   }

  
  Note:- You can use Alamofire or create your own request.
• Create your parameters to send request from your view controller to get your data in return of call back which you called.
  
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  var params = "Youur parameters" let networkManager = NetworkManager() networkManager.fetchData(params: params) { (responseObject:JSON?, error:Error?) in     if (error != nil) {         print("Error logging you in!")     } else {         print("Do something in the view controller in response to successful login!",responseObject! )     } }

  
  In responseObject, you will get your data using this callback.