Swift Language

Overview about the Swift Language

Details

On Xcode, go to File>New>Playground.
Choose iOS platform and the Blank template.
In this section, we can use the Playground to test out snippet of codes.

Constants, Variables, and Data Types

Constants and variables must be declared before they’re used. You declare constants with the let keyword and variables with the var keyword.

 let maximumNumberOfLoginAttemps = 10
var currentLoginAttempt = 0
 

You can declare multiple constants or multiple variables on a single line, separated by commas:

 var x = 0.0, y = 0.0, z = 0.0
 

Type annotations

You can provide a type annotation when you declare a constant or variable, to be clear about the kind of values the constant or variable can store.
Write a type annotation by placing a colon after the constant or variable name, followed by a space, followed by the name of the type to use.

 var welcomeMessage: String
 

Printing constants and variables

Swift uses string interpolation to include the name of a constant or variable as a placeholder in a longer string, and to prompt Swift to replace it with the current value of that constant or variable.
Wrap the name in parentheses and escape it with a backslash before the opening parenthesis:

 var friendlyWelcome = "Bonjour"
print("The current value of friendlyWelcome is \(friendlyWelcome)")
 

Semicolons

Unlike many other languages, Swift doesn’t require you to write a semicolon (;) after each statement in your code, although you can do so if you wish.
However, semicolons are required if you want to write multiple separate statements on a single line.

Most common types in Swift

Types:
- Integer
- Double
- Boolean (true, false)
- String
- Swift
You may have noticed that you don’t have to specify the type of value when you declare a constant or variable. This is called type inference.
Swift uses type inference to make assumptions about the type based on the value assigned to the constant or variable.

 let pi = 3.1415
 

 let pi: Double = 3.1414
 

Create your own type

 import UIKit

struct Car {
    var make: String
    var model: String
    var Year: Int
}

var c = Car(make: "BMW", model: "X3", year: 2022)
print (c.make)
 

Operators

Assignment:

 let jedi = "Luke"
 

Basic arithmetic

 var opponentScore = 3 * 8
print(opponentscore)
var myScore = 100 / 4
print(myScore)
 

Compound assignment

 myScore += 3
myScore -= 5
myScore *= 2
myScore /=2
 

Numeric type conversion

 let x = 3
let y = 0.1415
let pi = x + y /* not work */
let pi = Double(x) + y
 

Control Flow

Logical and comparison operators

==
!=
>
>=
<
<=
&&
||
!

if and if/else

 let temperature = 100
if temperature >= 100 {
    print("The water is boiling")
}
 

 var finished = 2
if finished == 1 {
    print("First place!") 
} else if finished == 2 {
    print("Second place!")
} else {
    print("Third place!")
}
 

Boolean values

 var isSnowing = false
if !ifSnowing {
    print("It is not snowing")
}
 

Switch statement

 let numberOfWheels = 2
switch numberOfWheels {
    case 0:
        print("Missing wheels!")
    case 1:
        print("Unicycle")
    case 2:
        print("Bicycle")
    case 3:
        print("Tricycle")
    case 4:
        print()"Cars!")
    default:
        print("Too many wheels!")
}
 

 let character = "z"
switch character {
    case "a", "e", "i", "o", "u":
        print("Vowels")
    default:
        print("consonant")
}
 

 switch distance {
    case 0...9:
        print("It is close")
    case 10...99:
        print("A bit further")
    case 100..999: 
        print("Quite far out")
    default:
        print("Let's call a cab")
}
 

Exercises

Grade calculation using if-else

Write a Swift program that takes a student’s numerical grade (0 to 100) as input and outputs the corresponding letter grade based on the following criteria:

A: 90-100
B: 80-89
C: 70-79
D: 60-69
F: Below 60

Template playground code:

 let grade = 95

//implement if-else logic here

Grade calculation using switch

Write a Swift program that takes a student’s numerical grade (0 to 100) as input and outputs the corresponding letter grade based on the following criteria:

A: 90-100
B: 80-89
C: 70-79
D: 60-69
F: Below 60

Template playground code:

 let grade = 95

//implement switch logic here

Grade calculation on app

Create a new app using the pokemon app from the introduction lecture as template
Modify it such as as a user enter the numeric grade, the corresponding letter grade is displayed
Bonus: display the letter grade using images!