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JOIN THIS COURSE FOR FREE:
As a programmer, it is our main job to deal with data: store, process, manipulate, share data.
This is what you do when building a social network apps to allow users share photos and videos. It’s the games you create with beautiful animation, graphics and stories.
Data comes in many forms. And as a developer, we all have to deal with a situation when data is not available.
It means that we have something to store but that thing is nothingness.
That’s why in Swift, we have a different “layer” of data type – Optional type.
It means that the type can store nothingness – empty data.
In this course, you’ll learn:
+ What is Optional and why we use Optional in Swift
+ How to create, and use Optional with unwrapping
+ Optional binding to safely unwrap optionals
+ Optional chaining
JOIN THIS COURSE FOR FREE:
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ABOUT CODE MASTERY
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Code Mastery is hosted by Duc Tran, founder of Developers Academy.
This is his free-style no notes, no teleprompter presentation and live coding broadcast with you guys everyday.
To join Duc’s free courses, register for free at
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MEET DUC TRAN
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Duc Tran is founder of Developers Academy, one of the world’s leading iOS, Android and Web development trainers.
More than 2,000,000 developers have studied his video trainings; 100,000 developers see his posts each month. Each year, Duc has helped 20,000 plus developers graduate from his online courses or video series.
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FREE TRAININGS IN IOS DEVELOPMENT
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SOURCE CODE IN THIS COURSE
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import UIKit
// 2.1 Introduce Optional
class GameViewController {
var questionLabel: UILabel?
var question: String
init(question: String, questionLabel: UILabel?) {
self.question = question
self.questionLabel = questionLabel
}
func viewDidLoad() {
// questionLabel!.text = question // this can crash
if questionLabel != nil {
questionLabel!.text = question
} else {
questionLabel = UILabel(frame: CGRect(x: 0, y: 0, width: 200, height: 40))
questionLabel!.text = question
}
}
}
let gameVC = GameViewController(question: “What is 5+5?”, questionLabel: nil) // this means there’s no label created
gameVC.viewDidLoad()
// 2.2 Optional Binding (if-let)
// introduction to Dictionary in Swift
var states: [String : String] = [
“CA” : “California”,
“LA” : “Los Angeles”,
“PA” : “Pennsylvania”,
“WA” : “Washington”,
“MA” : “Massachusetts”
]
let ca = states[“CA”]
let la = states[“LA”]
let pa = states[“PA”]
// but nil:
let ny = states[“NY”]
let tx = states[“tx”]
let key = “CA”
let state = states[key]
print(“(key) is (state)”)
if let caState = states[key] {
print(“(key) is (caState)”)
} else {
print(“Ooops. There’s no state matching this key”)
}
// another example:
var weatherForecast : [String : [String : Int]] = [
“today” : [
“temperature” : 92,
“humidity” : 98,
“rain” : 82
],
“tomorrow” : [
“temperature” : 72,
“humidity” : 12,
“rain” : 99
]
]
if let todayWeather = weatherForecast[“today”] {
if let temperature = todayWeather[“temperature”] {
print(“today’s temperature is (temperature)”)
}
}
// 2.3 Code Challenge
if let tomorrow = weatherForecast[“tomorrow”] {
if let rain = tomorrow[“rain”] {
print(rain)
}
}
var programs = [
“Total iOS Blueprint” : [“Swift”, “Build Foursquare”],
“Socialize Your Apps” : [“Build Facebook”, “Build Messenger”]
]
if let tibCourses = programs[“Total iOS Blueprint”] {
print(tibCourses[0])
}
// 2.4 Downside of if-let, introduce guard let syntax
var weatherForecast1 = [
“today” : [
“temperature” : 92,
“humidity” : 98
],
“tomorrow” : [
“temperature” : 72,
“rain” : 99
]
]
typealias WeatherDictionary = [String : [String : Int]]
struct CurrentWeather {
var temperature: Int
var humidity: Int?
var rain: Int?
}
// 1. Downside of if-let
func processWeather(for date: String, from weatherDictionary: WeatherDictionary) – CurrentWeather? {
if let today = weatherDictionary[date] {
if let temp = today[“temperature”], let humidity = today[“humidity”], let rain = today[“rain”] {
return CurrentWeather(temperature: temp, humidity: humidity, rain: rain)
} else {
return nil
}
} else {
return nil
}
}
func processWeather2(for date: String, from weatherDictionary: WeatherDictionary) – CurrentWeather? {
guard let today = weatherDictionary[date], let temp = today[“temperature”] else {
return nil
}
return CurrentWeather(temperature: temp, humidity: today[“humidity”], rain: today[“rain”])
}
// 2.5 Code Challenge
var fourSquareDatabase = [
“nearBy” : [
“1m” : [“Starbucks”, “Apple Bees”],
“5m” : [“Red Lobster”, “Sunny Cafe”]
]
]