Swift optional is empty or nil

example.swift

//
// check if array is empty or nil
//

class Example {
  func check(_ array: [String]?) {
    if (array ?? []).isEmpty == true {
      print("array is empty or nil")
    } else {
      print("array is not empty or nil")
    }
  }

  func example {
    check(nil) // => array is empty or nil
    check([]) // => array is empty or nil
    check(["abc"]) // => array is not empty or nil
  }
}

example2.swift

//
// check if class is nil, or class member is nil or empty
//

class Person {
  let name: String?
  init(name: String?) {
    self.name = name
  }
}

class Example2 {
  func check(_ person: Person?) {
    if (person?.name?.isEmpty ?? true) {     
      print("invalid")
    } else {
      print("valid")
    }
  }
  
  func example2 {
    check(nil) // => invalid
    check(Person(name: nil)) // => invalid
    check(Person(name: "")) // => invalid
    check(Person(name: "mei")) // valid
  } 
}

example3.swift

//
// check if class is nil, or class member is nil
//

class Person {
  let name: String?
  init(name: String?) {
    self.name = name
  }
}

class Example3 {
  func check(_ person: Person?) {
    if person?.name == nil {     
      print("invalid")
    } else {
      print("valid")
    }
  }
  
  func example3 {
    check(nil) // => invalid
    check(Person(name: nil)) // => invalid
    check(Person(name: "")) // => valid
    check(Person(name: "mei")) // valid
  } 
}

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