abstract - Swift - class method which must be overridden by subclass

Question

Is there a standard way to make a "pure virtual function" in Swift, ie. one that must be overridden by every subclass, and which, if it is not, causes a compile time error?

Answer 1

You have two options:

1. Use a Protocol

Define the superclass as a Protocol instead of a Class

Pro: Compile time check for if each "subclass" (not an actual subclass) implements the required method(s)

Con: The "superclass" (protocol) cannot implement methods or properties

2. Assert in the super version of the method

Example:

class SuperClass {
    func someFunc() {
        fatalError("Must Override")
    }
}

class Subclass : SuperClass {
    override func someFunc() {
    }
}

Pro: Can implement methods and properties in superclass

Con: No compile time check