Swift Programming Basics

# CHAPTER 3

Swift Programming Basics #

1. Introduction #

2. Learning Objectives #

• Understand the core syntax rules of Swift.

• Create single-line and multi-line comments.

• Utilize the print() function to debug code.

• Understand the concept of Variables and Constants at a high level.

• Work with basic data forms: Strings, Numbers, and Booleans.

3. Swift Syntax and Semicolons #

// This is JavaScript:
// let name = "Alice";

// This is Swift:
let name = "Alice" 

4. Comments in Swift #

// This is a single-line comment. I can write anything here!

/*
   This is a multi-line comment.
   It is great for writing long explanations
   or temporarily disabling chunks of code.
*/

5. The Print Statement #

// Printing a simple string
print("Hello, world!")

// Printing a number
print(42)

// Printing the result of math
print(10 + 5) // Will print 15

6. Variables and Constants (A High-Level Look) #

• If the box's contents *can change* later, we use var (Variable).

• If the box's contents *must never change*, we use let (Constant).

*(We will cover this deeply in the next chapter, but here is a quick overview!)*

// 1. Variable (var): The score changes as the game progresses!
var score = 0
score = 10
score = 25
print(score) // Prints 25

// 2. Constant (let): A user's birth year does not change.
let birthYear = 1990
// birthYear = 1995 -> ERROR! The compiler will block this.

7. Basic Data Forms #

Strings (Text): Always wrapped in double quotes "".

var playerName = "Arthur Morgan"
let greeting = "Welcome to the app!"

Numbers (Integers & Decimals): Written as raw numbers. No quotes!

var playerAge = 35         // Whole number (Integer)
let exactPi = 3.14159      // Decimal number

Booleans (True/False): The simplest form of logic. Used for on/off switches.

var isGameOver = false
let isProMember = true

8. Full Swift Snippet: A Mini Text Game Logic #

// 1. Setting up the game constants (Things that won't change)
let gameTitle = "Dragon Quest"
let maxHealth = 100

// 2. Setting up the variables (Things that will change)
var currentHealth = 100
var hasSword = false
var playerName = "Hero"

// 3. Simulating game events
print("Welcome to " + gameTitle)
print("Player spawned: " + playerName)

// The player finds a sword!
hasSword = true
print("Did the player find a sword?")
print(hasSword)

// The player takes damage!
currentHealth = currentHealth - 20
print("Player was attacked! Current health is:")
print(currentHealth)

9. Common Mistakes #

• Putting Quotes Around Variables: If you type print("currentHealth"), the computer will literally print the word "currentHealth". If you want the *value* stored inside the box (e.g., 80), you must drop the quotes: print(currentHealth).

• Misusing Case Sensitivity: Swift is strictly case-sensitive. var Score = 10 and var score = 10 are two completely different variables.

10. Best Practices #

• camelCase Naming: Always name your variables starting with a lowercase letter, and capitalize every subsequent word. (e.g., userEmailAddress, highestPlayerScore).

• Prefer let over var: Whenever possible, use let. It makes your code faster and prevents accidental bugs where you change data that shouldn't be changed. Only use var if you explicitly know the value will update.

11. Exercises #

1. 1. Write a single-line comment stating your name and today's date.

1. 2. Use the print() statement to output the result of 100 * 5.

12. Coding Challenges #

13. MCQ Quiz with Answers #

14. Interview Questions #

• Q: Explain the mechanical difference between a var and a let in Swift. Why does Apple heavily encourage the default use of let in iOS architecture?

• Q: Describe how Swift handles statement termination compared to legacy C-based languages. Are semicolons ever required in Swift?

• Q: Contrast a String literal with a variable reference inside a print() statement.

15. FAQs #

16. Summary #

17. Next Chapter Recommendation #