Example protocol-extension-generic

swift_protocol_extension_1.swift

//Declare class
class Cat {
    var name: String
    init(name: String) {
        self.name = name
    }
}

class Dog {
    var name:String
    init(name: String) {
        self.name = name
    }
}

//Protocol: get name 
protocol Pet {
    var name: String {get}  //all pets responds to a name
}