Polymorphism in Swift (if not) - swift

Question

I have this code in swift: To explain the idea of polymorphism!
//Polymorphism
class Person {
var name:String="Guest"
var age:Int=0
init(name:String) {
self.name=name
self.age=0
}
init(name:String, age:Int) {
self.name=name
self.age=age
}
func Update(name:String) {
self.name=name
}
func Upgrade() {
self.age++
}
}
class Student:Person
{
var average:Float=100
func IsOk()->Bool {
return average > 80
}
init(name:String, average:Float) {
super.init(name: name)
self.average=average
}
}
class Teacher:Person {
var Salary:Float=2000
init(name:String, age:Int, Salary:Float){
super.init(name: name, age: age)
self.Salary=Salary
}
func GetNetSalary()->Float {
return 0.8*self.Salary
}
override func Upgrade() {
super.Upgrade()
Salary*=1.1 // add 10% to salary
}
}
var t1:Teacher=Teacher(name: "Ahmed", age: 28, Salary: 3000)
var st1=Student(name:"Test", average: 70)
var p1:Person=Person(name: "abc")
var p2:Person=Student(name: "Student1", average: 100) //up casting
var p3:Person=Teacher(name: "Teacher", age: 40, Salary: 3008)
var arr=[t1, st1, p1, p2, p3] //array of persons and teachers and students
for instance in arr {
if instance is Student {println("This is student")}
if instance is Teacher {println("This is teacehr")}
}
In the end in the for loop How could I put such a condition to see if an element in the array is only a Person?
Because when I type:
if instance is Person {println("This is a Person")}
This gives me an error because this condition is always true!

Answer 1

EDITED
You are asking:
How could I put such a condition to see if an element in the array is only a Person?
In a strongly, statically, typed language in which you cannot access the run-time type of an object, you cannot do this. However, in Swift you can use the reflexive properties of the language, through the dynamicType method, to get such a type.

Answer 2

I should say that #Renzo's answer is outdated and dynamicType is deprecated. you must use type(of:) method for that. one more advice: if you want to know the exact type of an optional object, unwrap it first, then pass it to type(of:)
class A { }
class B: A { }
let b: A? = B()
print("\(type(of: b))") // you will get optional(A)
if let temp = b {
print("\(type(of: temp))") // you will get(B)
}

Answer 3

Try this:
for instance in arr {
if instance.dynamicType == Person.self {print("This is a Person")}
if instance.dynamicType == Student.self {print("This is student")}
if instance.dynamicType == Teacher.self {print("This is teacehr")}
}
More information about this you can find in Metatype Type chapter of documentation.

Answer 4

Maybe you can test if the element is aTeacher ? If not, it must be aPerson!