Swift optional chaining with non-nil value - swift

Question

I have the following program which works fine -
class Person {
var pet: Pet?
}
class Pet {
var name: String
var favoriteToy: Toy?
init(name: String) {
self.name = name
}
}
class Toy {
var name: String
init(name: String) {
self.name = name
}
}
let q = Person()
// Pet(name:"goofy")
// Toy(name:"teddy")
if let someToy = q.pet?.favoriteToy?.name {
print("This person's pet likes \(someToy).")
} else {
print("This person's pet does not have a favorite toy")
}
Prints:
This person's pet does not have a favorite toy
How to use the above code modified to print "This person's pet likes teddy."?
I know I will have not be able to use if let as there will be nothing to unwrap. So I have to write something like this instead of if let:
let someToy = q.pet.favoriteToy.name
print("This person's pet likes \(someToy).")
Should print "This person's pet likes the teddy."
I also know I have to put non-nil value something like this:
class Person {
var pet = Pet ()
}
Still I am having initialization problems. How to go about it?

Answer 1

This should solve your immediate needs...
let man = Person()
let goofy = Pet(name: "goofy")
let squeaky = Toy(name: "squeaky toy")
goofy.favoriteToy = squeaky
man.pet = goofy
But if a person is usually going to be initialized with a pet and a toy, and both of those classes are initialized with a string, then you might want to define a convenience initializer:
class Pet {
var name: String
var favoriteToy: Toy?
init(name: String) {
self.name = name
}
}
class Toy {
var name: String
init(name: String) {
self.name = name
}
}
class Person {
var pet: Pet?
convenience init(petName: String, toyName: String) {
self.init()
let toy = Toy(name: toyName)
let pet = Pet(name: petName)
pet.favoriteToy = toy
self.pet = pet
}
}
func test() {
let bill = Person(petName: "goofy", toyName: "squeaky ball")
guard let toyName = bill.pet?.favoriteToy?.name else { return }
print(toyName)
}
test()
One more thing: optional chaining can be combined with a guard statement to great effect in Swift.

Answer 2

Use ? = nil in your initializer to pass in some optional parameters.
class Person {
var pet: Pet?
init(pet: Pet? = nil) {
self.pet = pet
}
}
class Pet {
var name: String
var favoriteToy: Toy?
init(name: String, toy: Toy? = nil) {
self.name = name
self.favoriteToy = toy
}
}
class Toy {
var name: String
init(name: String) {
self.name = name
}
}
let q = Person(pet: Pet(name: "goofy", toy: Toy(name: "teddy")))
// Pet(name:"goofy")
// Toy(name:"teddy")
if let someToy = q.pet?.favoriteToy?.name {
print("This person's pet likes \(someToy).")
} else {
print("This person's pet does not have a favorite toy")
}