swift ios

func myFunc( externalParameterName   internalParameterName : Type) {               print( internalParameterName ) } //externalName and interName can be same so when we call function... func myFunc( external : value) //if you wanted to omit the external parameter func myFunc(_  internalParameterName : Type){     print( internalParameterName ) } //call function func myFunc(value)

// //   ViewController.swift //   BMI Calculator // //   Created by Angela Yu on 21/08/2019. //   Copyright © 2019 Angela Yu. All rights reserved. // import UIKit class CalculateViewController : UIViewController {          var bmiValue : String = "0.0"     var calculateBrain = CalculateBrain ()          @IBOutlet weak var heightLabel : UILabel !     @IBOutlet weak var weightLabel : UILabel !     @IBOutlet weak var heightSlider : UISlider !     @IBOutlet weak var weightSlider : UISlider !          override func viewDidLoad () {         super . viewDidLoad ()         // Do any additional setup after loading the view.     }     @IBAction func heightSliderChange ( _ sender: UISlider ) {         let height = String (format: "%.1f" , sender. value )   ...

1. Force unwrapping     optional !  2. Check for nial value     if optional != nil {      optional !     } 3. Optional Binding     if let safeOptional = optional{    safeOptional     } 4. Nil coalescing Operator    optional ?? defaultValue 5. Optional Chaining   optional ? .property //if optional is not nil then .proerty

Controller //    ViewController.swift //    Quizzler-iOS13 // //    Created by Angela Yu on 12/07/2019. //    Copyright © 2019 The App Brewery. All rights reserved. // import  UIKit class   ViewController :  UIViewController  {      var   quizBrain  =  QuizBrain ()           @IBOutlet   weak   var   scoreLabel :  UILabel !      @IBOutlet   weak   var   questionLabel :  UILabel !      @IBOutlet   weak   var   trueButton :  UIButton !      @IBOutlet   weak   var   falseButton :  UIButton !      @IBOutlet   weak   var   progressBar :  UIProgressView !           override   func   viewDidLoad () {          super . viewDidLoad ()       ...