as! से अनिवार्य कास्टिंग और उसके जोखिम

class Animal {
    let name: String
    init(name: String) { self.name = name }
}
class Dog: Animal {
    func bark() -> String { return name + " says Woof" }
}
class Cat: Animal {
    func meow() -> String { return name + " says Meow" }
}
let a: Animal = Dog(name: "Rex")
// let cat = a as! Cat  // would crash at runtime
print("Only force-cast when certain")

class Animal {
    let name: String
    init(name: String) { self.name = name }
}
class Dog: Animal {
    func bark() -> String { return name + " says Woof" }
}
class Cat: Animal {
    func meow() -> String { return name + " says Meow" }
}
let a: Animal = Dog(name: "Rex")
if a is Dog {
    let dog = a as! Dog
    print(dog.bark())
}

class Animal {
    let name: String
    init(name: String) { self.name = name }
}
class Dog: Animal {
    func bark() -> String { return name + " says Woof" }
}
class Cat: Animal {
    func meow() -> String { return name + " says Meow" }
}
func barkIfDog(_ a: Animal) {
    guard a is Dog else { return }
    let dog = a as! Dog
    print(dog.bark())
}
barkIfDog(Dog(name: "Rex"))

class Animal {
    let name: String
    init(name: String) { self.name = name }
}
class Dog: Animal {
    func bark() -> String { return name + " says Woof" }
}
class Cat: Animal {
    func meow() -> String { return name + " says Meow" }
}
let a: Animal = Dog(name: "Rex")
let safe = a as? Dog
let forced = a as! Dog
print(safe?.bark() ?? "nil")
print(forced.bark())

class Animal {
    let name: String
    init(name: String) { self.name = name }
}
class Dog: Animal {
    func bark() -> String { return name + " says Woof" }
}
class Cat: Animal {
    func meow() -> String { return name + " says Meow" }
}
let animals: [Animal] = [Dog(name: "Rex"), Dog(name: "Buddy")]
let dogs = animals as! [Dog]
for d in dogs { print(d.bark()) }

class Animal {
    let name: String
    init(name: String) { self.name = name }
}
class Dog: Animal {
    func bark() -> String { return name + " says Woof" }
}
class Cat: Animal {
    func meow() -> String { return name + " says Meow" }
}
let animals: [Animal] = [Dog(name: "Rex"), Cat(name: "Mia")]
// let dogs = animals as! [Dog] // would crash on the Cat
for a in animals {
    if let d = a as? Dog { print(d.bark()) }
}

class Animal {
    let name: String
    init(name: String) { self.name = name }
}
class Dog: Animal {
    func bark() -> String { return name + " says Woof" }
}
class Cat: Animal {
    func meow() -> String { return name + " says Meow" }
}
let a: Animal = Dog(name: "Rex")
let viaOptional = (a as? Dog)!
let viaForce = a as! Dog
print(viaOptional.name, viaForce.name)

class Animal {
    let name: String
    init(name: String) { self.name = name }
}
class Dog: Animal {
    func bark() -> String { return name + " says Woof" }
}
class Cat: Animal {
    func meow() -> String { return name + " says Meow" }
}
func process(_ a: Animal) -> String {
    if let d = a as? Dog { return d.bark() }
    return "not a dog"
}
print(process(Dog(name: "Rex")))
print(process(Cat(name: "Mia")))

class Animal {
    let name: String
    init(name: String) { self.name = name }
}
class Dog: Animal {
    func bark() -> String { return name + " says Woof" }
}
class Cat: Animal {
    func meow() -> String { return name + " says Meow" }
}
let known: Animal = Dog(name: "Rex")
if known is Dog {
    print((known as! Dog).bark())
}

class Animal {
    let name: String
    init(name: String) { self.name = name }
}
class Dog: Animal {
    func bark() -> String { return name + " says Woof" }
}
class Cat: Animal {
    func meow() -> String { return name + " says Meow" }
}
let a: Animal = Dog(name: "Rex")
if a is Dog { print((a as! Dog).bark()) } else { print("safe skip") }