Sort array by calculated distance in Swift

Question

So I have an array of custom objects which have a Double latitude and Double longitude value. I would like to sort the array based on the calculated distance from a specific

Answer 1

Another way to approach this problem is to make an extension on Array that allows you to sort by location. The benefit to this approach is that the call site is a lot cleaner and easier to understand.

** NOTE ** - I have changed the class to a struct. However this will work just fine with a class as well.

struct Place {
    var latitude: CLLocationDegrees
    var longitude: CLLocationDegrees

    var location: CLLocation {
        return CLLocation(latitude: self.latitude, longitude: self.longitude)
    }

    func distance(to location: CLLocation) -> CLLocationDistance {
        return location.distance(from: self.location)
    }
}

Then we declare an extension like so where the Element of the array is a Place:

extension Array where Element == Place {

    mutating func sort(by location: CLLocation) {
         return sort(by: { $0.distance(to: location) < $1.distance(to: location) })
    }

    func sorted(by location: CLLocation) -> [Place] {
        return sorted(by: { $0.distance(to: location) < $1.distance(to: location) })
    }
}

This allows us to then sort by location using the following syntaxes:

places.sort(by: myLocation) // mutating version

let newPlaces = places.sorted(by: myLocation) // non mutating version

Answer 2

Assuming you have a model Place for your objects:

class Place {
    var latitude: CLLocationDegrees
    var longitude: CLLocationDegrees

    var location: CLLocation {
        return CLLocation(latitude: self.latitude, longitude: self.longitude)
    }

    func distance(to location: CLLocation) -> CLLocationDistance {
        return location.distance(from: self.location)
    }
}

Then an array var places: [Place] can be sorted as such:

places.sort(by: { $0.distance(to: myLocation) < $1.distance(to: myLocation) })

Answer 3

Thats quite easy to do. Your function which calculate the distance must take two parameter of type what is in your array you want to sort and return Bool, for example:

// I assumed your array stores MyLocation
func mySortFunc(location1: MyLocation, location2: MyLocation) -> Bool {

    // do your calculation here and return true or false
}

var array: [MyLocation] = ...
array.sortInPlace { (loc1, loc2) -> Bool in
    mySortFunc(loc1, location2: loc1)
}