FabP93

func urlSession(_ session: URLSession, didReceive challenge: URLAuthenticationChallenge, completionHandler: @escaping (URLSession.AuthChallengeDisposition, URLCredential?) -> Void) {
    guard
      challenge.protectionSpace.authenticationMethod == NSURLAuthenticationMethodServerTrust,
      let serverTrust = challenge.protectionSpace.serverTrust
    else {
        completionHandler(URLSession.AuthChallengeDisposition.cancelAuthenticationChallenge, nil)
        return
    }
    
    guard

FabP93

extension Key: Hashable {
  func hash(into hasher: inout Hasher) {
    hasher.combine(self.id)
  }
  
  func hash(into hasher: inout Hasher) {
    hasher.combine(self.id)
  }
}

FabP93

let key1 = Key(id: 1, title: "Key1")
let key2 = Key(id: 1, title: "Key2")
dict[key1] = 1058
dict[key2] = 368
print(dict.count) // 2
print(key1 == key2) // false
print(key1.hashValue == key2.hashValue) // true

FabP93

struct Key {
  let id: Int
  let title: String
}

extension Key: Hashable {
  func hash(into hasher: inout Hasher) {
    hasher.combine(self.id)
  }
}

FabP93

// Using hasher. Actually, you will never use it directly.
var hasher = Hasher()
hasher.combine("Hello")
hasher.combine("World")
hasher.combine(2020)
let hashValue = hasher.finalize()

// This is the correct way to implement Hashable.
extension YourStruct: Hashable {
  func hash(into hasher: inout Hasher) {

FabP93

/// A point in an x-y coordinate system.
struct GridPoint {
    var x: Int
    var y: Int
}

extension GridPoint: Hashable {
    static func == (lhs: GridPoint, rhs: GridPoint) -> Bool {
        return lhs.x == rhs.x && lhs.y == rhs.y
    }

FabP93

let pushups = Array<Pushup>()
// This doesn't raise any error because built-in
// generic types are covariant.
var exercises: Array<Exercise> = pushups

FabP93

struct Activity<T> {}

var pushup = Activity<Pushup>()

// You can't do this, it raises the error:
// Cannot assign value of type 'Activity<Pushup>' to type 'Activity<Exercise>'
var activity: Activity<Exercise> = pushup

FabP93

class Exercise {
  func perform() {}
  func stop() {}
}

class Pushup: Exercise {
  override func perform() {}
  override func stop() {}
}

FabP93

private func handleSharedFile() {
  // extracting the path to the URL that is being shared
  let attachments = (self.extensionContext?.inputItems.first as? NSExtensionItem)?.attachments ?? []
  let contentType = kUTTypeData as String
  for provider in attachments {
    // Check if the content type is the same as we expected
    if provider.hasItemConformingToTypeIdentifier(contentType) {
      provider.loadItem(forTypeIdentifier: contentType,
                        options: nil) { [unowned self] (data, error) in
      // Handle the error here if you want