Nested Callbacks in Swift 3.0

Nested Callbacks

If you don’ t know how to create callbacks in swift you can visit my previous blogs click here.

Need of nested callbacks. Suppose you hit a request to network manager using callback and get request result in back in the controller and send a data to ViewModel and want back data again in the controller. Most of we use to inform NotificationCenter to inform the controller that data is stored in the object after that we reload table view, collection view or draw view to represent data on the screen.The better is that we create the callbacks so its saves our lots of time creating a notification using NotificationCenter and also save us to remember the each notification names. Example of creating nested callback:-

typealias ServiceResponse = (JSON?, Error?) -> Void

class NetworkManager: NSObject {
    func fetchData(params : String , _ completion: @escaping ServiceResponse) -> Void {

        completion( yourdata  ,  error as NSError )
    }
}

let networkManager = NetworkManager()
networkManager.fetchData(params: params) { (responseObject:JSON?, error:Error?) in
    print(responseObject)
}

typealias ServiceResponse = (JSON?, Error?) -> Void

class NetworkManager: NSObject {

func fetchData(params : String , _ completion: @escaping ServiceResponse) -> Void {

completion( yourdata , error as NSError )

}

let networkManager = NetworkManager()

networkManager.fetchData(params: params) { (responseObject:JSON?, error:Error?) in

print(responseObject)

}

Example of fetching data in the above by creating another callback in it or you can say that creating a nested callback:-

class ViewModel : NSObject {
     func getValue( jsonData : JSON , completion: ((_ data: Bool) -> Void) )  {
         // Perfome some actions
          completion(true)
     }
}

let networkManager = NetworkManager()
fileprivate let ViewModelObject = ViewModel()

networkManager.fetchData(params: params) { (responseObject:JSON?, error:Error?) in
    print(responseObject)
    self.storeViewModelObject.getValue(jsonData: responseObject!)  {
        (data : Bool) in
        print(data)
        self.tableView.reloadData()
    }
}

class ViewModel : NSObject {

func getValue( jsonData : JSON , completion: ((_ data: Bool) -> Void) ) {

// Perfome some actions

completion(true)

}

let networkManager = NetworkManager()

fileprivate let ViewModelObject = ViewModel()

networkManager.fetchData(params: params) { (responseObject:JSON?, error:Error?) in

print(responseObject)

self.storeViewModelObject.getValue(jsonData: responseObject!) {

(data : Bool) in

print(data)

self.tableView.reloadData()

}

If you don’ t know how to create callbacks in swift you can this blog

Use Callbacks in Swift in place of Delegates

bhavuk chawla 5 February 2018

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Nested Callbacks in Swift 3.0

Nested Callbacks

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