Extensions

Overview

Extensions in Swift can:

• Add computed instance properties and computed type properties
• Define instance methods and type methods
• Provide new initializers
• Define subscripts
• Define and use new nested types
• Make an existing type conform to a protocol

Extensions affect all future and existing instances of the extended type.

Syntax:

extension SomeType {
  // extends functionality of SomeType
}

extension SomeType: Protocol1, Protocol2 {
  // extends SomeType with protocol conformance
}

Example

extension Int {
  var squared: Int {
    self * self
  }
}

print(10.squared)