CODEWITHSUNDEEP
javaandroidiosswiftdelegates
iSofia
iSofia

Reputation: 1532

Implementing delegates within the class (iOS/Swift)

In mobile development, interfaces and delegates are implemented as follows (using the location service as an example):

1. Android, Java

    public class myClass implements LocationListener {      
        @Override
        public void onLocationChanged(Location location) {          
        }
        @Override
        public void onStatusChanged(String s, int i, Bundle bundle) {
        }   
    }

1. iOS, Swift

    class myVC: UIViewController, CLLocationManagerDelegate {
        func locationManager(manager: CLLocationManager, 
                             didUpdateLocations locations: [CLLocation]) {
        }
    }

What would be the iOS/Swift equivalent of this type of Android implementation:

2. Android, Java

    public class myClass {      
        LocationListener GPS = new LocationListener() {
            @Override
            public void onLocationChanged(Location location) {          
            }
            @Override
            public void onStatusChanged(String s, int i, Bundle bundle) {
            }               
        }
    }

2. iOS, Swift?

    class myVC: UIViewController {
       ???
    }

I'm not academically-trained, so my programming lingo is really bad. Could anyone also please help explain the differences between these two types of implementations, and what they are called?

Much TIA.

Upvotes: 0

Views: 203

Answers (2)

Anita Nagori
Anita Nagori

Reputation: 747

If you want to enhance how location work with IOS then you can do by this way

Add these lines in Info.plist

<key>NSLocationUsageDescription</key>
<string></string>
<key>NSLocationWhenInUseUsageDescription</key>
<string></string>

Step : 1 

Declare the delegate in class where you need location update
Let say 

class LocationPickerViewController: CLLocationManagerDelegate

1.1 - Declare the locationManager object 

let locationManager = CLLocationManager()

Step : 2

Define one method where you configure all this for Location method
let say

func setupLocationAcess()
{
   locationManager = CLLocationManager()
   locationManager.delegate = self
   locationManager.requestWhenInUseAuthorization()
   locationManager.desiredAccuracy = kCLLocationAccuracyBest
   locationManager.startUpdatingLocation()
}

Step : 3 Define this method to viewWillAppear

Step : 4 Implement delegate method in your class

public func locationManager(_ manager: CLLocationManager, didUpdateLocations 
locations: [CLLocation]) 
{
    guard let location = locations.first else { return }
    currentLocationListeners.forEach { $0.action(location) }
    currentLocationListeners = currentLocationListeners.filter { !$0.once }
    manager.stopUpdatingLocation()
}

I hope it will help you

Upvotes: 0

R.B.
R.B.

Reputation: 423

In Swift, a protocol, such as CLLocationManagerDelegate provides a blueprint of "stuff" that a class, struct or enum must implement to say it "conforms" to that specific protocol. (It could also have optional methods that are not required to be implemented.)

In your first example:

class myVC: UIViewController, CLLocationManagerDelegate { }

myVC is saying that it implements/conforms-to protocol CLLocationManagerDelegate. For this, it must implement any required methods of that protocol and might implement any optional ones too; such as locationManager(_:didUpdateLocations:).

If I understand your question, you would like to know if you might end up implementing myClass without saying it implements CLLocationManagerDelegate. Something like this:

class myVC: UIViewController {
   var locationManagerDelegate = SomethingImplementingTheDelegate()
}

class SomethingImplementingTheDelegate: CLLocationManagerDelegate {
    func locationManager(manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) { /*...*/ }
}

As you can see, you still need some class/struct/enum that implements what the protocol/delegate CLLocationManagerDelegate says, since (a protocol) it's just a blueprint.

(Technical note: Protocols can provide some implementation through protocol extensions, but it is for conforming types, you still can't instantiate a protocol).

Upvotes: 1

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