Swift in as as! The difference between as?

As: Type consistent or sub-class

This value is only matched if the type of a value is the same as the specified type at runtime (runtime) and the right of the as mode-or subclass of that type. If the match succeeds, the type of the value being matched is converted to as the pattern specified on the left side of the pattern.

class Animal {} class  = as Animal

as! Parent class strong Rotor class

class Animal {} class  =as! Dog

No more! Compile will error

As? Conversion failure returns nil

class Animal {} class Dog:animal {} class  =as!  as? Dog

Animal as! The Dog compiler will error the as?

Swift in as as! The difference between as?