Protocols are about things we want to be used in common. So it can be called a kind of feature definition.
// Here I will use the Hackingwithswift example
protocol Identifiable {
var id: String { get set } // We have a property called id
}
struct User: Identifiable {
var id: String // We have a structure with the id property
}
func displayID(thing: Identifiable) { // And here a struct with id property is requested.
print("My ID is \(thing.id)")
}
displayID(thing: User.init(id: "Mehmet")) // And here a struct with id property is passed to it// Protocols can also inherit. Here again, let's continue with the hackingwithswift example.
protocol Payable {
func calculateWages() -> Int
}
protocol NeedsTraining {
func study()
}
protocol HasVacation {
func takeVacation(days: Int)
}
protocol Employee: Payable, NeedsTraining, HasVacation { } // Our new protocol inheriting from 3 different protocols.
struct Work : Employee{ // In this structure, we use the inherited protocol
// And Xcode automatically creates the functions we need to create for us.
func calculateWages() -> Int {
return 4000
}
func study() {
print("Working")
}
func takeVacation(days: Int) {
print("You have \(days) days vacation")
}
}
let mehmet = Work()
mehmet.calculateWages() // 4000
mehmet.study() // Working
mehmet.takeVacation(days: 15) // You have 15 days vacation// Extensions allow you to add features to an existing type.
extension Double {
func multiply(times : Double) -> Double {
return self * times
}
}
let num1 = 5.0
print(num1.multiply(times: 5)) // 25
// We've added a multiplication feature to the Double type
// And we also added factorial calculation
extension Double {
func factorial() -> Double {
let number = self
var result = 1.0
for i in 1...Int(number){
result *= Double(i)
}
return result
}
}
print(num1.factorial()) // 120// Let's explain again through hackingwithswift example
// Since sequences and series are collected under the collections protocol in swift,
// we can create a feature to be used for both by adding an extension to the collection protocol.
let pythons = ["Eric", "Graham", "John", "Michael", "Terry", "Terry"]
let beatles = Set(["John", "Paul", "George", "Ringo"])
extension Collection { // So we can use this plugin in both types
func summarize() {
print("There are \(count) of us:")
for name in self {
print(name)
}
}
}
// Works well on both
pythons.summarize()
beatles.summarize()// This is a really difficult subject to understand.
// So for sure, I suggest you listen to this part and then do the questions.
protocol Identifiable {
var id: String { get set }
func identify()
}
extension Identifiable {
func identify() {
print("My ID is \(id).") // Preparing the function for automatic id creation
}
}
struct User: Identifiable { // So look at this struct
// It doesn't have such function but it has inheritance and that inheritance also has a plugin
var id: String
}
let twostraws = User(id: "twostraws")
twostraws.identify() // So that the extension of that inheritance can be used in the objects of this structure.