Using convenience init in subclasses (Swift)

Question

I'm using Playground in Xcode, and my objects aren't being initialized with their names. I feel like it's because I'm using the convenience init incorrectly in my sublcasses, and I was wondering what is the proper way to use them in subclasses. I've read the other similar questions, but I think my question is different in the way that it has overriding inits and convenience inits.

class Animal
{
    var name:String

    init(name:String)
    {
        self.name = name
    }

    convenience init() { self.init(name: "") }

    func speak() { }
}

class Fox: Animal
{
    override init(name: String)
    {
        super.init(name: name)
    }

    convenience init() { self.init(name: "Fox") }

    override func speak()
    {
        println("Ring")
    }
}

class Cat: Animal
{
    override init(name: String)
    {
        super.init(name: name)
    }

    convenience init() { self.init(name:"Cat") }

    override func speak() {
        println("Meow")
    }
}

class Dog: Animal {
    override init(name: String) {
        super.init(name: name)
    }

    convenience init()
    {
        self.init(name:"Dog")
    }

    override func speak() {
        println("Woof")
    }
}

let animals = [ Dog(), Cat(), Fox()]
for animal in animals
{
    animal.speak()
}

Answer 1

There are no errors in your code. I think the problems is to understand how the Xcode's playground works. probably you had pressed "show results" icon and you're watching at something like this:

but this is telling us that the "Module name" dot "Class name" of the three animals; the prefix __lldb_expr_25 ( in my picture ) is not an error but a dynamic module name that is ok in playground.

Indeed you should look at the "assistant editor":

to see the output of speck() method:

This can be even more pronounced with a slight modification to the code:

so the output is:

Answer 2

Let me answer according to what I understand so far -

override inits is like overriding the same to same super class init method. Here you can't add an extra behaviour as a init method parameter such as:

class Animal
{
    var name:String

    init(name:String)
    {
        self.name = name
    }

    func speak() { }
}

class Cat: Animal
{
    override init(name: String)
    {
        super.init(name: name)
    }

    override func speak() {
        println("Meow")
    }
}

convenience inits is like custom init method of subclass means if you want to implement a init method into your sub-class but with some extra behaviours along with the super class init method. such as:

class Animal
    {
        var name:String

        init(name:String)
        {
            self.name = name
        }

        func speak() { }
    }

    class Cat: Animal
    {
        var type: String = "Maine Coons"
        convenience init(type:string, name: String)
        {
            self.type = type
            self.init(name: name)
        }

        override func speak() {
            println("Meow")
        }
    }

I hope it will help you. Thanks