Calling and printing object inside object in swift 2

I have 2 classes, I have cats object in the AnimalClass and I am parsing jSON and I want to initialize the cats name from the jSON

class AnimalClass: NSObject {

    var cats = [catClass]()
    ..... 
}

And

class catClass: NSObject {

var name : String = ""

init(data : NSDictionary)
{
    if let add = data["name"] as? String
    {
        self.name = add
    }

Here I am trying to initialize it in the ViewController.swift

    var animals = [AnimalClass]()
for(var i = 0; i < data_array.count; i++)
{
    if let add = data_array[i] as? NSDictionary
    {
      self.animals.append(AnimalClass(data: add)) // this works
      self.animals.cats.append(AnimalClass(data: add)) // this doesn't work
    }
}

My question is for this line self.animals.cats.append(AnimalClass(data: add)) how can append to cats object which is in the AnimalClass.