Subscript script, class extension, subscript script Extension

Subscript script, class extension, subscript script Extension

Subscript scripts and class extensions

//// ViewController. swift // subscript script _ class extension import UIKitclass ViewController: UIViewController {override func viewDidLoad () {super. viewDidLoad () let testString = "helloworld" print (testString []) // reference the methods and packages in the subscript script // extensions file if let tempstring = testString. test () {print (tempstring) }}// extended extension String {// 1. script subscript (start: Int, length: Int)-> String {// only the get method is available. You can omit get {} let index1 = self . Index (self. startIndex, offsetBy: start) let index2 = self. index (index1, offsetBy: length) let range = Range (uncheckedBounds: (lower: index1, upper: index2) return self. substring (with: range)} func test ()-> String? {Return "test "}}