What does the “required” keyword in Swift mean?

Question

Take the following example:

class A {
    var num: Int

    required init(num: Int) {
        self.num = num
    }
}

class B: A {
    func haveFun() {
              


        

Answer 1

“The use of the required modifier ensures that you provide an explicit or inherited implementation of the initializer requirement on all subclasses of the conforming class, such that they also conform to the protocol.”

Excerpt From: Apple Inc. “The Swift Programming Language (Swift 2).” iBooks. https://itun.es/us/jEUH0.l