how to store an array of type cllocationcoordinate2d in nsuserdefaults in swift 2.0

Question

i want to save an array of location coordinates in nsuserdefaults.how to do that

Martin Wildfeuer · Accepted Answer

This is indeed not to easy. You are hitting two limitations:
1. You cannot store an array of CLLocationCoordinate2D to UserDefaults directly
As the following excerpt of the UserDefaults (https://developer.apple.com/reference/foundation/userdefaults) describes, you cannot directly store an array [CLLocationCoordinate2D] to UserDefaults. Allowed are only combinations of [Int], [String] etc.

The NSUserDefaults class provides convenience methods for accessing
common types such as floats, doubles, integers, Booleans, and URLs.
A default object must be a property list—that is, an instance of (or for
collections, a combination of instances of): NSData, NSString, NSNumber,
NSDate, NSArray, or NSDictionary. If you want to store any other type of
object, you should typically archive it to create an instance of NSData.
For more details, see Preferences and Settings Programming Guide.

In order to store and retrieve custom objects to/from UserDefaults, you have to utilize NSKeyedArchiver (https://developer.apple.com/reference/foundation/nskeyedarchiver) and NSKeyedUnarchiver. However...
2. NSKeyedArchiver does not work for CLLocationCoordinate2D
I won't go into detail here why this does not work, however it does work for CLLocation which conforms to NSSecureCodingand thus can be archived. Therefore, one solution would be to convert [CLLocationCoordinate2D] to [CLLocation] before storing it to UserDefaults and vice-versa when retrieving them. The following example should work as expected. 
```swift
import CoreLocation
// Store an array of CLLocationCoordinate2D
func storeCoordinates(_ coordinates: [CLLocationCoordinate2D]) {
    let locations = coordinates.map { coordinate -> CLLocation in
        return CLLocation(latitude: coordinate.latitude, longitude: coordinate.longitude)
    }
    let archived = NSKeyedArchiver.archivedData(withRootObject: locations)
    UserDefaults.standard.set(archived, forKey: "coordinates")
    UserDefaults.standard.synchronize()
}
// Return an array of CLLocationCoordinate2D
func loadCoordinates() -> [CLLocationCoordinate2D]? {
    guard let archived = UserDefaults.standard.object(forKey: "coordinates") as? Data,
        let locations = NSKeyedUnarchiver.unarchiveObject(with: archived) as? [CLLocation] else {
            return nil
    }
let coordinates = locations.map { location -> CLLocationCoordinate2D in
    return location.coordinate
}

return coordinates
}
```
Please note that this will not in Playgrounds as UserDefaults are only available in sandboxed environments.
Now let's test our implementation:
```swift
let testCoordinates = [
    CLLocationCoordinate2D(latitude: 0.123456789, longitude: 0.123456789),
    CLLocationCoordinate2D(latitude: 1.123456789, longitude: 1.123456789),
    CLLocationCoordinate2D(latitude: 2.123456789, longitude: 2.123456789)
]
storeCoordinates(testCoordinates)
let coordinates = loadCoordinates()
dump(coordinates)
```
Hope that helps :)

Jaisan mathew · Answer

thanks martin....:)

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Jaisan mathew

Jaisan mathew

how to store an array of type cllocationcoordinate2d in nsuserdefaults in swift 2.0

2 Answers

Martin Wildfeuer

Martin Wildfeuer

1. You cannot store an array of CLLocationCoordinate2D to UserDefaults directly

2. NSKeyedArchiver does not work for CLLocationCoordinate2D

Jaisan mathew

Jaisan mathew