Why self.title = title doesn't work around 4:20?

Hi taisuke araki,

In Swift and other languages alike, class inheritance only does so much when creating an instance of a child class that extends a parent class. In Swift, the compiler is always running which evaluates code in real-time. The reason we simply can't just call self.title is because the class Clothing doesn't have a property called title, we could try adding it but that would cause an error because it's already declared in the Product class.

Why does system consider the constant self.title is already set?

As mentioned above, Swift doesn't assume that self.title is set, it complains because you're attempting to set a value for a property that doesn't exist within Children therefore we first need to call super.init and pass our title through in order to set a value for it.

Think of the compiler as a safe guard, it's always looking out for us and ensuring that from a high level that our code is working to an extent but not entirely.

Hope that helps.