Skip to content

Instantly share code, notes, and snippets.

Embed
What would you like to do?
iOS Companion Playground to Accompany the Third Post on Extensions
import PlaygroundSupport
import UIKit
import MapKit
// This can be messy. It will work, but...ick:
extension Array {
// ERROR: This will not work
// var description: String {
// return self.joined(separator: ",")
// }
// Simple CSV line.
var description1: String {
if let selfie = self as? [String] { // Filter for a certain type of element.
return selfie.joined(separator: ",") // Now, since it's a String, we can join the party.
}
return "UN-STRING" // This is not a joiner.
}
// Creates a CSV string from multiple contained Arrays.
var description: String {
if let selfie = self as? [String] { // Simple CSV.
return selfie.joined(separator: ",")
} else if let selfie = self as? [[String]] { // An Array of Arrays of String can be CSVed.
return selfie.reduce(into: [String]()) { (accumulator: inout [String], element) in // Pile each line on top of the other.
let line = element.description // This asks each line to render as CSV.
accumulator.append(line)
}.joined(separator: "\n") // Join the lines by linefeeds.
}
return "HUH?" // Can't CSV.
}
}
// These are test datasets for the CSV functionality.
let testArray0 = [["One", "Two", "Three"],["Four", "Five", "Six"],["Seven","eight","Nine"]]
let testArray1 = ["One", "Two", "Three"]
let description = testArray0.description1 // Contains "UN-STRING"
let description0 = testArray1.description1 // Contains "One,Two,Three"
let description1 = testArray0.description // Contains "One,Two,Three\nFour,Five,Six\nSeven,eight,Nine"
let description2 = testArray1.description // Contains "One,Two,Three"
let csv0 = testArray0.description // Contains "One,Two,Three\nFour,Five,Six\nSeven,eight,Nine"
let csv1 = testArray0[0].description // Contains "One,Two,Three"
let csv2 = testArray1.description // Contains "One,Two,Three"
// Now, with type-constrained extensions, we can get the same functionality with drastically less code.
extension Array where Element == String {
var csvLine: String { // Since this is type-constrained, we don't need to take a selfie.
return self.joined(separator: ",")
}
}
extension Array where Element == [String] {
var csv: String {
return self.reduce(into: [String]()) { (accumulator: inout [String], element) in
let element2 = element.csvLine
accumulator.append(element2)
}.joined(separator: "\n")
}
}
let csv3 = testArray0.csv // Contains "One,Two,Three\nFour,Five,Six\nSeven,eight,Nine"
let csv4 = testArray0[0].csvLine // Contains "One,Two,Three"
let csv5 = testArray1.csvLine // Contains "One,Two,Three"
// This demonstrates the capability using a protocol. We extend Array for elements of the Equatable protocol.
extension Array where Element: Equatable {
mutating func removeObject(object: Element) { // This allows us to remove an object by value.
if let index = self.firstIndex(of: object) {
self.remove(at: index)
}
}
}
// These tests apply to the above protocol-based extension.
var testArray = [1,2,3,4,5,6,7,8,9,0]
testArray.removeObject(object: 6)
let newArray = testArray // Contains [1,2,3,4,5,7,8,9,0]
var testArray2 = ["1", "2", "3", "4", "5", "6", "7", "8", "9", "0"]
testArray2.removeObject(object: "6")
let newArray2 = testArray2 // Contains ["1", "2", "3", "4", "5", "7", "8", "9", "0"]
var testArray3 = [["1", "2", "3"], ["4", "5", "6"], ["7", "8", "9"]]
testArray3.removeObject(object: ["4", "5", "6"])
let newArray3 = testArray3 // Contains [["1", "2", "3"], ["7", "8", "9"]]
var testArray4 = [CLLocationCoordinate2D(latitude: 36, longitude: -77), CLLocationCoordinate2D(latitude: 26, longitude: -80), CLLocationCoordinate2D(latitude: -26, longitude: 33)]
// This will not work. CLLocationCoordinate2D is not Equatable
//testArray4.removeObject(object: CLLocationCoordinate2D(latitude: 26, longitude: -80))
extension Array where Element == CLLocationCoordinate2D {
/* ################################################################## */
/**
- returns: An MKMapRect, containing all the points in the Array.
Nil, if the Array has less than 2 points, or does not contain coordinates.
*/
var rect: MKMapRect! {
if 1 < self.count {
let result = self.reduce(into: (maxLong: -180, maxLat: -180, minLong: 180, minLat: 180)) { (result: inout (maxLong: Double, maxLat: Double, minLong: Double, minLat: Double), inLocationCoords) in
result.maxLong = Swift.max(inLocationCoords.longitude, result.maxLong)
result.maxLat = Swift.max(inLocationCoords.latitude, result.maxLat)
result.minLong = Swift.min(inLocationCoords.longitude, result.minLong)
result.minLat = Swift.min(inLocationCoords.latitude, result.minLat)
}
let topLeft = MKMapPoint(CLLocationCoordinate2D(latitude: result.maxLat, longitude: result.minLong))
let bottomRight = MKMapPoint(CLLocationCoordinate2D(latitude: result.minLat, longitude: result.maxLong))
let size = MKMapSize(width: abs(bottomRight.x - topLeft.x), height: abs(bottomRight.y - topLeft.y))
return MKMapRect(origin: topLeft, size: size)
}
return nil
}
/* ################################################################## */
/**
- returns: The center coordinate of the group of coordinates.
*/
var center: CLLocationCoordinate2D! {
let result = self.reduce(into: (maxLong: -180, maxLat: -180, minLong: 180, minLat: 180)) { (result: inout (maxLong: Double, maxLat: Double, minLong: Double, minLat: Double), inLocationCoords) in
result.maxLong = Swift.max(inLocationCoords.longitude, result.maxLong)
result.maxLat = Swift.max(inLocationCoords.latitude, result.maxLat)
result.minLong = Swift.min(inLocationCoords.longitude, result.minLong)
result.minLat = Swift.min(inLocationCoords.latitude, result.minLat)
}
return CLLocationCoordinate2D(latitude: (result.maxLat + result.minLat) / 2, longitude: (result.maxLong + result.minLong) / 2)
}
/* ################################################################## */
/**
- returns: A coordinate span, encompassing all of the coordinates in the Array.
Nil, if the span cannot be calculated for any reason.
*/
var span: MKCoordinateSpan! {
if 1 < self.count {
let result = self.reduce(into: (maxLong: -180, maxLat: -180, minLong: 180, minLat: 180)) { (result: inout (maxLong: Double, maxLat: Double, minLong: Double, minLat: Double), inLocationCoords) in
result.maxLong = Swift.max(inLocationCoords.longitude, result.maxLong)
result.maxLat = Swift.max(inLocationCoords.latitude, result.maxLat)
result.minLong = Swift.min(inLocationCoords.longitude, result.minLong)
result.minLat = Swift.min(inLocationCoords.latitude, result.minLat)
}
return MKCoordinateSpan(latitudeDelta: result.maxLat - result.minLat, longitudeDelta: result.maxLong - result.minLong)
}
return nil
}
/* ################################################################## */
/**
- returns: A region, encompassing all of the elements in the Array.
Nil, if the region cannot be calculated for any reason.
*/
var region: MKCoordinateRegion! {
if let center = self.center, let span = self.span {
return MKCoordinateRegion(center: center, span: span)
}
return nil
}
}
extension CLLocationCoordinate2D {
init(_ inLocationArray: [CLLocationCoordinate2D]) {
self.init(latitude: inLocationArray.center.latitude, longitude: inLocationArray.center.longitude)
}
}
// Example dataset:
let washingtonMonument = CLLocationCoordinate2D(latitude: 38.9072, longitude: -77.0369)
let whiteHouse = CLLocationCoordinate2D(latitude: 38.8977, longitude: -77.0365)
let capitolBuilding = CLLocationCoordinate2D(latitude: 38.8899, longitude: -77.0091)
let lincolnMemorial = CLLocationCoordinate2D(latitude: 38.8893, longitude: -77.0502)
let jeffersonMemorial = CLLocationCoordinate2D(latitude: 38.8814, longitude: -77.0365)
let airAndSpaceMuseum = CLLocationCoordinate2D(latitude: 38.8882, longitude: -77.0199)
let ronaldReaganAirport = CLLocationCoordinate2D(latitude: 38.8512, longitude: -77.0402)
let pentagon = CLLocationCoordinate2D(latitude: 38.8719, longitude: -77.0563)
let arlingtonCemetery = CLLocationCoordinate2D(latitude: 38.8783, longitude: -77.0687)
let airAndSpaceMuseumAnnex = CLLocationCoordinate2D(latitude: 38.9109, longitude: -77.4442)
let arrayOfCoordinates = [washingtonMonument,
whiteHouse,
capitolBuilding,
lincolnMemorial,
jeffersonMemorial,
airAndSpaceMuseum,
ronaldReaganAirport,
pentagon,
arlingtonCemetery,
airAndSpaceMuseumAnnex
]
let rectThatWillEncloseAllLocations = arrayOfCoordinates.rect // Remember that this is in map points (not coordinates), so the numbers will be big:
// left: 76471147.05123556
// top: 102675876.5094804
// width: 324434.0747377872
// height: 57184.79726368189
let greatLocationForAHotel = arrayOfCoordinates.center // This will contain (38.88105, -77.22665000000001), which is a mean of all the data points in the Array.
let aSpanThatIsBigEnoughForEverything = arrayOfCoordinates.span // This contains (0.05969999999999942, 0.4350999999999914), which is in long/lat coordinates.
let aRegionThatFitsEverything = arrayOfCoordinates.region // This is a region, made up of the center and span. It will enclose all the points.
let anotherGreatLocationForAHotel = CLLocationCoordinate2D(arrayOfCoordinates) // In this trick, we simply assign the center (38.88105, -77.22665000000001) to the property.
// This should display the map, centered, with markers for each location.
class MapViewController: UIViewController {
var mapView: MKMapView!
override func viewDidLoad() {
super.viewDidLoad()
self.mapView = MKMapView()
self.view.addSubview(self.mapView)
}
override func viewDidLayoutSubviews() {
super.viewDidLayoutSubviews()
self.mapView.frame = self.view.bounds
self.mapView.mapType = .standard
self.mapView.removeAnnotations(self.mapView.annotations)
arrayOfCoordinates.forEach { [unowned self] coordinate in
let annotation = MKPointAnnotation()
annotation.coordinate = coordinate
self.mapView.addAnnotation(annotation)
}
self.mapView.setRegion(self.mapView.regionThatFits(arrayOfCoordinates.region), animated: true)
}
}
let controller = MapViewController()
PlaygroundPage.current.liveView = controller
PlaygroundPage.current.needsIndefiniteExecution = true
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment