How can I allow my function to accepts two different objects in swift?

Question

I have a function which takes one argument. I wanted my function to accept two object types. How can I do it? Here is the example below:

func accept(user: Customer) {
  ...
}

It should accept Customer and Employee object reference.

accept(objRefCustomer)
accept(objRefEmployee)

Please help me in this case.

Answer 1

Alternative to super-classing: use protocols

You needn't necessarily use a superclass for this case (if Customer and Employee are struct value types; superclass option is not possible), but can rather use the more generic approach of protocols.

Define a protocol Users which blueprints properties and methods for your Customer and Employee instances (if we let Customer and Employee conform to Users, then we promise that instances of these two structures will have accessible the blueprinted properties and methods):

protocol Users {
    var name: String { get }
    func printTypeOfUser()
}

Define the Customer and Employee structures, and their conformance to the protocol Users:

struct Customer : Users {
    let name: String
    init(name: String) { self.name = name }

    func printTypeOfUser() {
        print("Is a Customer!")
    }
}

struct Employee : Users {
    let name: String
    let id: Int
    init(name: String, id: Int) { self.name = name; self.id = id }
    
    func printTypeOfUser() {
        print("Is an Employee!")
    }
}

Now you can define a generic function where its generic, say T, is type constrained to types conforming to the protocol Users, which in this case is equivalent to the Customer or Employee types

func accept<T: Users>(user: T) {
    print("Name of user: \(user.name) [\(user.dynamicType)]")
    user.printTypeOfUser()
    
    // do something additional employee-specific if user is an employee?
    if let employee = user as? Employee {
        print("User is an employee with id: \(employee.id)")
    }
}

Example usage of this function for Employee as well as Customer instances:

let employee = Employee(name: "John", id: 1)
let customer = Customer(name: "Sarah")

accept(employee) /* Name of user: John [Employee] 
                    Is an Employee!
                    User is an employee with id: 1 */

accept(customer) /* Name of user: Sarah [Customer]
                    Is a Customer!                 */