#core location

CLLocationManager Refactor | Xcode 11 | Swift 5.2 | KtrKathir

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CLLocationManager Refactor | Core Location | Xcode 11 | Swift 5.2 | KtrKathir

In this swift tutorial I discuss the topic of LocationManager Refactor out of your UIViewController. This will make your code much more readable, and keep those UIViewController small.

This video Contains How to implement a LocationManager as a singleton class and fetch a location from where every you…

In iOS The user's location is kept private, so to use it there needs to be asked for permission. In this tutorial the steps required to ask for permission will be described. This tutorial is made with Xcode 10 and built for iOS 12.

Open Xcode and create a new Single View App.

For product name, use IOSRequestPermissionTutorial and then fill out the Organization Name and Organization Identifier with your customary values. Enter Swift as Language and choose Next.

Go to the Storyboard. Drag a button to the main view. Double-click the button and change the title to "Get Location".  The Storyboard will look like this.

Open the Assistant Editor and make sure the ViewController.swift file is visible. Ctrl and drag from the Button to the ViewController class to create the following Action.

Go to the ViewController.swift file and add the following line to import the CoreLocation framework.

import CoreLocation

Conform the ViewController class to the CLLocationManagerDelegate protocol. Change the class declaration line to

class ViewController: UIViewController, CLLocationManagerDelegate {

Add the following property

let locationMgr = CLLocationManager()

The  CLLocationManager is the object that will give you the GPS coordinates. Next, implement the getLocation(_:) method.

@IBAction func getLocation(_ sender: Any) { // 1 let status = CLLocationManager.authorizationStatus() switch status { // 1 case .notDetermined: locationManager.requestWhenInUseAuthorization() return // 2 case .denied, .restricted: let alert = UIAlertController(title: "Location Services disabled", message: "Please enable Location Services in Settings", preferredStyle: .alert) let okAction = UIAlertAction(title: "OK", style: .default, handler: nil) alert.addAction(okAction) present(alert, animated: true, completion: nil) return case .authorizedAlways, .authorizedWhenInUse: break } // 4 locationManager.delegate = self locationManager.startUpdatingLocation() }

The authorizationStatus returns the current authorisation status.

The when in use authorisation get location updates while the app is in the foreground

When location services is disabled, the user will be shown an alert

Send location updates to the delegate, which is the View Controller.

Next, implement the CLLocationManager delegate methods.

// 1 func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) { if let currentLocation = locations.last { print("Current location: \(currentLocation)") } } // 2 func locationManager(_ manager: CLLocationManager, didFailWithError error: Error) { print(error) }

The current location is printed to the console.

An Error is generated and displayed when the location can't get updated.

To enable the permissions for location updates while the app is running a special key is needed. Open info.plist. Right-click and select Add Row. Enter the following Values.

Build and Run the project, When the app ask for permission 

Turn on the Location Arrow in the console and select a predefined location. The current location gps coordinates will be displayed on the console.

Current location: <+51.50998000,-0.13370000> +/- 5.00m (speed -1.00 mps / course -1.00) @ 9/12/16, 3:25:27 PM Central European Summer Time Current location: <+51.50998000,-0.13370000> +/- 5.00m (speed -1.00 mps / course -1.00) @ 9/12/16, 3:25:28 PM Central European Summer Time Current location: <+51.50998000,-0.13370000> +/- 5.00m (speed -1.00 mps / course -1.00) @ 9/12/16, 3:25:29 PM Central European Summer Time Current location: <+51.50998000,-0.13370000> +/- 5.00m (speed -1.00 mps / course -1.00) @ 9/12/16, 3:25:30 PM Central European Summer Time Current location: <+51.50998000,-0.13370000> +/- 5.00m (speed -1.00 mps / course -1.00) @ 9/12/16, 3:25:31 PM Central European Summer Time Current location: <+51.50998000,-0.13370000> +/- 5.00m (speed -1.00 mps / course -1.00) @ 9/12/16, 3:25:32 PM Central European Summer Time

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There are changes in location manager in iOS 8 and it's all tackled here:

This is how you know GPS accuracy on iOS. The shorter the value, the better GPS accuracy it has. The value indicated is in meters.

Create a new project with a class prefix of "CA".

In the interface file, CAViewController.h:

@interface CAViewController: UIViewController {     CLLocationManager *locationManager }

In the implementation file, CAViewController.m:

locationManager = [[CLLocationManager alloc] init]; [locationManager setDesiredAccuracy:kCLLocationAccuracyBest]; [locationManager startUpdatingLocation];

CLLocationManager can be assigned a delegate property. This is the object to which CLLocationManager sends messages.

A delegate receives all event messages from a particular object.

The delegate need only implement methods that correspond to the events it wants to hear about.

In this case we are setting the delegate to self (a CAViewController instance), and it receives events from CLLocationManager.

Add the following line under the first in CAViewController.m:

[locationManager setDelegate:self];

locationManager now sends locationManager:didUpdateToLocation:fromLocation and other messages to its delegate, CAViewController (referred to as self above).

Therefore we can implement didUpdateToLocation in CAViewController.m:

- (void)locationManager:(CLLocationManager *)manager       didUpdateToLocation:(CLLocation *)newLocation       fromLocation:(CLLocation *)oldLocation {     NSLog(@"%@", newLocation); }

And also:

- (void)locationManager:(CLLocationManager *)manager        didFailWithError:(NSError *)error {     NSLog(@"Could not find location: %@, "error); }

An object can only send its delegate messages from a specific set listed in a protocol. The delegate implements methods from the protocol for the events that it is interested in.

Here is the protocol for CLLocationManagerDelegate:

@protocol CLLocationManagerDelegate <NSObject> @option - (void)locationManager:(CLLocationManager *)manager     didUpdateToLocation:(CLLocation *)newLocation         fromLocation:(CLLocation *)oldLocation; - (void)locationManager:(CLLocationManager *)manager     didFailWithError:(NSError *)error; @end

 <NSObject> at the end of the protocol header indicates that CLLocationManagerDelegate includes all of the methods in the NSObject protocol as well.

The protocol is not a class - it is simply a list of methods.

A class that implements methods from a protocol conforms to it.

By default, protocol methods must be implemented in a conforming class.

Optional methods can be indicated using the @optional directive. Before sending an optional message, the object first asks its delegate if it is okay to send first a respondsToSelector: message. This method checks at runtime whether an object implements a given method.

- (void)finishedFindingLocation:(CLLocation *)newLocation {     if ([[self delegate[ respondsToSelector:@selector(locationManager:didUpdateToLocation:fromLocation:)])     {         [[self delegate] locationManager:self             didUpdateToLocation:newLocation                 fromLocation:oldLocation];     }

If a protocol method is not marked as optional, is not implemented, yet called, an unrecognized selector exception will be thrown.

Explicitly state that a class conforms to a protocol:

@interface CAViewController : UIViewController <CLLocationManagerDelegate>

This is how you get your location in iOS. The answer by Flea is the one I used:

I spent the day reading Big Nerd Ranch's Guide to iOS and learning about delegation, protocol methods, core location, the mapkit framework, debugging, and the build phases for creating an iOS app.  And I ate a cream puff.  It was tasty.

Delegation is an object oriented approach to callbacks.  You assign a delegate which is responsible for receiving all the event messages of a particular object.  The delegate may then store, manipulate, and act upon those messages.  A cream puff is a pastry ball filled with whipped cream, ice cream, or pastry cream.

A protocol is simply a list of methods.  They're useful primarily as a means of ensuring that certain methods be utilized, regardless of the the class the object is a part of.  In order for an object to be able to have a delegate, it also must have a protocol that declares the messages that the object can send to it's delegate.  A cream puff is also known as a profiterole or if you're a fancy french person, a choux à la crème.

Core location is a framework that allows the developer to use the devise's geographical location.  Mapkit is a framework that allows the developer to display that information in map form on the devise.  The cream puff I got had a caramel filling, but vanilla and chocolate were also offered.

Debugging in objective C involves setting a lot of break points and stepping through as necessary to find the offending lines of code.  Once you've reached a break point, your code is effectively paused and you may query for additional information such as the value of various properties.  This proves very useful, and coupled with Xcode's helpful warnings, makes debugging almost as easy as smacking a tv to get better reception.  It is rumored, but not confirmed, that the cream puff originated in Northern Italy.