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iOS

Endi Hıdır
Endi Hıdır
1,762 Points
Posted by Endi Hıdır
Endi Hıdır
1,762 Points

My question about Casting Types in Swift

class Animal {}
class Dog: Animal {}

let a: Animal = Dog()

a as! Dog

This is Downcasting but Why can't we use normal casting like this: Dog(a) or Dog(a)!

I know "as" is using for converting from a class to one of its subclasses. But I can't understand why second method doesn't work ? Can someone explain the reason please.

1 Answer

Micah Howard
Micah Howard
23,770 Points
Micah Howard
Micah Howard
23,770 Points

Hi Endi,

I am not sure where you are in the iOS coursework available on Treehouse, but I will attempt to answer your question. In your example, Dog is a subclass of Animal. This means that all of the properties and methods in the Animal class are inherited by the Dog class. So, you just have to assign the "Dog" class to the constant "a". "a" will be both a "Dog" and an "Animal". I hope this helps!

class Animal {}
class Dog: Animal {}

let a = Dog()