When creating a subclass, do I have to initialize ?

I find initialization can get a bit confusing, what with member wise initializers, default initializers, convenience initializers, inherited initializers, failable initializers, etc., and all the rules surrounding them.

But the bottom line is what's stated right at the beginning of Apple's documentation: "Classes and structures must set all of their stored properties to an appropriate initial value by the time an instance of that class or structure is created. Stored properties cannot be left in an indeterminate state." https://developer.apple.com/library/mac/documentation/Swift/Conceptual/Swift_Programming_Language/Initialization.html

Another issue is that Treehouse's challenge editor sometimes is a bit quirky. You didn't give a link so I can't see exactly what it wanted, but sometimes even an extra space will defeat it.

Consider this code:

class Student {
    private var name: String

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

}

class UnderGrad: Student {

}

var joe = UnderGrad(name: "Bob")

An initializer is not needed for UnderGrad because it introduces no new stored properties (instance variables in other languages). So the inherited initializer works fine. It meets the rule: every stored property (viz., name) is given a value.

Now consider this:

class Student {
    private var name: String

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

}

class UnderGrad: Student {
    private var grade: Int

    init(name:String, grade: Int) {
        self.grade = grade
        super.init(name: name)
    }

}

var joe = UnderGrad(name: "Bob", grade: 12)

Here, because UnderGrad introduces a new stored property grade, that property has to be initialized when an UnderGrad is created. Since the inherited initializer can't do it, UnderGrad has to have its own, which initializes grade and then calls the superclass's initializer to initialize name.

Hope this helps.