callback function from caller to callee in swift - ios

Question

I have a view controller and a class for doing the bits to call the services and get the data from server.
The ViewController code is below,
class ViewController : UIViewController
{
override func viewDidLoad() {
let parser = Parser()
parser.connectServer("abc URL" , ..... <gotDataFromServer> ..... )
}
func gotDataFromServer(response:String)
{
...... Do our things here .......
}
}
and the parser code is below,
class Parser
{
func connectServer(apiURL:String,...<call back function name>...)
{
let manager = RequestOperationManager.sharedManager()
manager.GET(apiURL ,
parameters: nil,
success: { (operation,responseObject) ->Void in
.....<Call back the function which is passed in parameter> ....
},
failure: { (operation , error) in
print ("error occurred")
})
}
}
Now in the above sample code i want to pass call back function "gotDataFromServer" as a parameter and when the inner function get the response from the server then i want to call this function back.
Can anyone please help.

Answer 1

You can use delegates to achieve that. Try out following code
class ViewController : UIViewController, DataDelegate
{
override func viewDidLoad() {
let parser = Parser()
parser.delegate = self
parser.connectServer("abc URL" , ..... <gotDataFromServer> ..... )
}
func gotDataFromServer(response:String)
{
...... Do our things here .......
}
}
And add protocol in parser as follows
protocol DataDelegate {
func gotDataFromServer(response:String)
}
class Parser
{
var delegate : DataDelegate!
func connectServer(apiURL:String,...<call back function name>...)
{
let manager = RequestOperationManager.sharedManager()
manager.GET(apiURL ,
parameters: nil,
success: { (operation,responseObject) ->Void in
delegate.gotDataFromServer("") //parameter is your data
},
failure: { (operation , error) in
print ("error occurred")
})
}
}

Answer 2

Here's an example how you can do it using closure
class Parser {
func connectServer(apiURL: String, completion: String -> Void) {
// ... make call, get data
// share the results via completion closure
completion("data")
}
}
class ViewController: UIViewController {
override func viewDidLoad() {
let parser = Parser()
// Option #1
parser.connectServer("mybackend.com/connect") {
print("received data \($0)")
}
// Option #2 is the same as Option #1 but a bit longer
parser.connectServer("mybackend.com/connect") { (data) -> Void in
print("received data \(data)")
}
// Option #3 - Or if you have a separate funciton
// be careful with retain cycle
parser.connectServer("mybackend.com/connect", completion: gotDataFromServer)
}
func gotDataFromServer(response:String) { }
}