Fetch posts from firebase by location with swift - swift

Question

I'm trying to fetch posts and print them to the console when the user comes into some sort of radius of them. How can I do this in swift.

Answer 1

Here's a small struct in Swift I wrote that let's you compute the distance in km between two coordinates using the Haversine formula
.
Example
let london = Coordinate(long: -0.118092, lat: 51.509865)
let paris = Coordinate(long: 2.3522219, lat: 48.856614)
print(london.distance(to: paris)) // ~343.43km
print(london == paris) // false
print(london) // 51.509865,-0.118092
print(paris) // 48.856614,2.3522219
Code
import Foundation
public struct Coordinate: CustomStringConvertible, Equatable {
// Earth radius in km
private static let radiusEarth = 6371.0
public typealias Distance = Double
public let lon: Double
public let lat: Double
public init(long: Double, lat: Double) {
self.lon = long
self.lat = lat
}
public static func == (lhs: Coordinate, rhs: Coordinate) -> Bool {
return lhs.lon == rhs.lon && lhs.lat == rhs.lat
}
public var description: String {
return "\(lat),\(lon)"
}
// Haversine formula
public func distance(to other: Coordinate) -> Distance {
let dLat = deg2rad(other.lat - lat)
let dLon = deg2rad(other.lon - lon)
let a =
sin(dLat / 2) * sin(dLat / 2) +
cos(deg2rad(lat)) * cos(deg2rad(other.lat)) *
sin(dLon / 2) * sin(dLon / 2)
let c = 2 * atan2(sqrt(a), sqrt(1 - a))
return Coordinate.radiusEarth * c
}
private func deg2rad(_ deg: Double) -> Double {
return deg * (.pi / 180.0)
}
}