Swift - Extensions

• Swift extensions can add fields, functions, and initializers to all the named types!
  • Swift named types:
    • class
    • struct
    • enum
    • protocol

Protocol and Extensions

• The extensions have even more power with protocols!
  • We can extend a named type so that it conforms to a protocol.
  • We can define a default method implementation for a protocol.

Protocol default methods implementations

Consider this:

classDiagram
    Animal <|.. Dog
    class Animal {
        +name: String
        +speak()
    }
    class Dog {
        +name: String
        +speak()
    }

We can define a default implementation for speak() by defining an extension:

protocol Animal {
  var name: String { get }
  init(name: String)
  func speak()
}

extension Animal {
  func speak() {
    print("I'm an animal!")
  }
}