Calculate the distance between 2 coordinates

Distance.swift

extension Float {
    var radians: Float {
        get {
            return self * Float(M_PI / 180.0)
        }
    }
}

struct Location {
    let radius: Float = 3961.0
    let latitude: Float
    let longitude: Float

    init(lat: Float, long: Float) {
        latitude = lat
        longitude = long
    }

    func distance(location: Location) -> Float {
        let lat_1 = latitude.radians
        let lat_2 = location.latitude.radians
        let lng_1 = longitude.radians
        let lng_2 = location.longitude.radians
        let dlon = lng_2 - lng_1
        let dlat = lat_2 - lat_1
        let a = pow(sin(dlat / 2.0), 2.0) + cos(lat_1) * cos(lat_2) * pow(sin(dlon / 2.0), 2.0)
        let c = 2.0 * atan2(sqrt(a), sqrt(1.0 - a))
        return radius * c
    }
}

let loc_1 = Location(lat: 33.942536, long: -118.408075)
let loc_2 = Location(lat: 32.733556, long: -117.189667)

loc_1.distance(loc_2)