Add try catch and convert a function to a generic class swift - ios

Question

In one of my view controllers I have a function to establish a tcp connection , send and receive messages which is as follows.
func tcpConnection(host: NSString){
var client = TCPClient(addr: String(host) as String, port: Config.tcpPort)
let (success, err) = client.connect(timeout: Config.tcpConnectionTimeout)
log?.debug("Connected \(success)")
guard success else { log?.error("Cannot Connect \(err)"); return}
let (successMsg, failmsg) = client.send(str: self.jsonString)
let data = client.read(Config.expectedByteLength)
guard let d = data else { return }
guard let recievedMsg = String(bytes: d, encoding: NSUTF8StringEncoding) else { return }
self.recivedMsgFromServer = recievedMsg
log?.debug("Recieved msg\(recievedMsg)")
let (clientClosed, errormsg) = client.close()
guard clientClosed else { return }
}
I am using this piece of code twice in the same view controller. So I want to have a generic class for this function . Also I have many guards which I want to replace with a single try catch block.
Also after receiving a message I am doing different things in both the tcp connection functions.
Following is what I have tried until now.
class TcpService{
var jsonString : String = ""
func tcpConnection(host: NSString){
do {
var client = try TCPClient(addr: String(host) as String, port: Config.tcpPort)
let (success, err) = client.connect(timeout: Config.tcpConnectionTimeout)
log?.debug("Connected \(success)")
guard success else { log?.error("Cannot Connect \(err)"); return}
let (successMsg, failmsg) = client.send(str: self.jsonString)
let data = client.read(Config.expectedByteLength)
guard let d = data else { return }
guard let recievedMsg = String(bytes: d, encoding: NSUTF8StringEncoding) else { return }
log?.debug("Recieved msg\(recievedMsg)")
/*Do Something different in every viewController
//For Example
self.Info = Mapper<Info>().map(recievedMsg)
log?.debug("Status\(self.Info?.Status)")
*/
let (clientClosed, errormsg) = client.close()
guard clientClosed else { return }
} catch {
let fetchError = error as NSError
print(fetchError)
// Handle Error
}
}
}
When I try to call this function from the new class in my view controller it does not behave in the same way the function in the view controller did.
Is there anything I should change in the way I have created the class?
Any help will be appreciated as I am very new to swift. Thank you

Answer 1

This is a way your problem could be solved. Skip the custom error throwing part if you don't actually need it. The way to refactor it is using callback function, just send your function into this one, i.e.:
TCPService.connect("some_host", message: "your_message") { response in
Mapper<Info>().map(response)
}
Code:
import Foundation
extension NSError {
static func error(with localized: String) -> NSError {
return NSError(domain: "error", code: 2, userInfo: [NSLocalizedDescriptionKey: localized])
}
}
class TCPService {
static func connect(host: String, andSend message: String, onComplete: String -> ()) {
do {
let client = try TCPClient(addr: host, port: Config.tcpPort)
let (successfulConnection, error) = client.connect(timeout: Config.tcpConnectionTimeout)
log?.debug("Connected \(successfulConnection)")
guard successfulConnection else {
throw NSError.error(with: error)
log?.error("Cannot Connect \(error)")
return
}
let (successfullySent, failureMessage) = client.send(str: message)
let data = client.read(Config.expectedByteLength)
guard successfullySent,
let d = data,
receivedMessage = String(bytes: d, encoding: NSUTF8StringEncoding) else {
throw NSError.error(with: failureMessage)
return
}
log?.debug("Received msg\(receivedMessage)")
onComplete(receivedMessage)
let (clientClosed, errorMessage) = client.close()
guard clientClosed else {
throw NSError.error(with: errorMessage)
return
}
} catch let error as NSError {
let fetchError = error as NSError
print(fetchError)
// Handle errors
}
}
}