Unable to understand behaviour of inheritance in swift? - ios

Question

I have created a parent class which has one property. Now i'm inheriting this class into my child class. It is obvious that member of parent class will become member of child class. So, when i change the value in child class, the same variable value is also getting changed in parent class.
I have used below mentioned code.
class SomeClass {
var avar:String = "Hello"
var bvar:String?
func someFunc() {
}
}
class Bclass:SomeClass {
func myFunc() {
self.avar = "Bye"
super.avar
}
}
let c = Bclass()
c.myFunc() // "Bye"
let d = SomeClass()
d.someFunc() // "Hello"
Here output is Bye but it should be Hello as i'm not changing parent class member value. When i access with instance of SomeClass then it shows output as Hello
Few questions-
Does it make copy of parent class variable in child class or refrence?
super means i want to access variable of parent class then why value changed ?
EDIT: As per Frankie answer
In below scenario why it still prints "Hello".
class SomeClass {
var avar:String = "Hello"
var bvar:String?
func someFunc() {
self.avar
}
}
class Bclass:SomeClass {
func myFunc() {
self.avar = "Bye"
super.avar
self.avar
}
}
class Cclass:SomeClass {
func myFunc() {
super.avar
self.avar
}
}
let c = Bclass()
c.myFunc()
let d = SomeClass()
d.someFunc()
let e = Cclass()
e.myFunc()

Answer 1

When you create an instance with let c = Bclass() there is one and only one instance created. There is no 'super instance' that is additionally created, so the notion of copying or reference doesn't make sense.
The subclass merely inherits all the properties and functions of the super class, or more plainly, it inherits only what defines the super class. Therefore self.avar and super.avar are the exact same thing.
Example:
class SomeClass {
var avar: String = "Hello"
}
class Bclass: SomeClass {
//imagine there is a (var avar: String = "Hello") here because it was defined in the super class
func myFunc() {
print(super.avar) //prints 'Hello'
self.avar = "Bye"
print(super.avar) //prints 'bye'
}
}
EDIT
From the OP's edit:
let c = Bclass()
c.myFunc() //assigns self.avar = "Bye", therefore prints "Bye"
let d = SomeClass()
d.someFunc() //does not make any assignment in someFunc, therefore prints the assigned value of "Hello"
let e = Cclass()
e.myFunc() //does not make any assignment in myFunc, therefore 'e' looks to its
//superclass for the value since it was never overridden and prints "Hello"
//It does NOT look to 'c' for the value because 'c' is a completely separate instance

Answer 2

A subclass takes all of the properties, function and methods of its superclass. The superclass is some kind of starting place / foundation for a subclass.
For instance, when you create a normal ViewController, you define it as:
class mySubclass: UIViewController{
// UIViewController's variables, properties, methods, functions...
// your code
}
You can imagine that all of the code from the superclass now lies inside the subclass as well. A good example of usage might be:
class Person{
var name: String = ""
var age: Int = 0
var job: String? = ""
}
class John: Person {
self.name = "John" // equivalent of super.name
self.age = 26
self.job = "Programmer"
}
You can say that the second class is some kind of customisation for the superclass, copying and changing its properties.