How to sort properties by class?

Question

I'm just a beginner and learn basics, so I have such a task:

1. Create "Animals" class and its properties
2. Create "Plants" class and its properties
3. Put all of it in array and sort it by name and class

I tried to do it like this:

class Animals {
    var dog: Dog? = Dog()
    var cat: Cat? = Cat()
}
class Dog {
    let dog1 = "Brungilda"
}
class Cat {
    let cat1 = "Kuzya"
}

class Plants {
    var grass: Grass? = Grass()
    var flowers: Flowers? = Flowers()
}
class Grass {
    let grass1 = "Mentha"
}
class Flowers {
    let flower1 = "Rose"
}

let animals = Animals()
let plants = Plants()

var allIn = [Any]()

allIn.append(animals.cat?.cat1)
allIn.append(animals.dog?.dog1)
allIn.append(plants.flowers?.flower1)
allIn.append(plants.grass?.grass1)

type(of: allIn[0]) // Optional <String>.Type

BUT the type of all properties is Optinal String, so I don't understand how to make it correct(2 types of properties: Animals and Plants), moreover I don't understand how to sort it by these types.

I guess my way of how to do the task is totally wrong. I'll be glad if somebody can explain me or even show the right way.