Operators, Conditions, and Loops

# CHAPTER 5

Operators, Conditions, and Loops #

1. Introduction #

2. Learning Objectives #

• Perform mathematical calculations using Arithmetic Operators.

• Compare data using Comparison and Logical Operators (==, !=, &&, ||).

• Write conditional branching logic using if, else if, and else.

• Write clean multi-condition logic using the switch statement.

• Execute repetitive code using for-in and while loops.

3. Arithmetic and Assignment Operators #

• Addition: +

• Subtraction: -

• Multiplication: *

• Division: /

• Remainder (Modulo): % (Returns the remainder of a division)

Compound Assignment: A shortcut for updating a variable!

var score = 10
score += 5   // Exact same as: score = score + 5
score -= 2   // Exact same as: score = score - 2
print(score) // Prints 13

4. Comparison and Logical Operators #

• Equal to: ==

• Not equal to: !=

• Greater / Less than: >, <, >=, <=

Logical Operators (Combining conditions):

• AND (&&): BOTH sides must be true.

• OR (||): AT LEAST ONE side must be true.

• NOT (!): Flips the boolean (True becomes False).

let age = 20
let hasTicket = true

// true AND true -> Results in true!
let canEnter = (age >= 18) && hasTicket 

5. Conditional Statements (if / else) #

let userAge = 16

if userAge >= 18 {
    print("Welcome to the app!")
} else if userAge >= 13 {
    print("Welcome, teen user. Parental controls enabled.")
} else {
    print("Sorry, you are too young to use this app.")
}

6. The switch Statement (Cleaner Conditions) #

let weather = "Rain"

switch weather {
case "Sunny":
    print("Wear sunglasses 🕶️")
case "Rain":
    print("Bring an umbrella ☔️")
case "Snow":
    print("Wear a heavy coat ⛄️")
default:
    print("Check the forecast later.")
}

7. The for-in Loop #

• 1...5 (Closed Range): 1, 2, 3, 4, 5

• 1..<5 (Half-Open Range): 1, 2, 3, 4

// This will print the phrase exactly 5 times!
for i in 1...5 {
    print("This is iteration number \(i)")
}

// If you don't need the number 'i', use an underscore '_' to save memory!
for _ in 1...3 {
    print("Hello!")
}

8. The while Loop #

var countdown = 3

while countdown > 0 {
    print("\(countdown)...")
    countdown -= 1 // We MUST decrease it, or it will loop forever!
}
print("BLASTOFF! 🚀")

9. Mini Project: Grade Calculator #

let mathScore = 85
let scienceScore = 92
let englishScore = 78

// 1. Operators: Calculate the average
let totalScore = mathScore + scienceScore + englishScore
let average = totalScore / 3

print("Your average score is \(average)")

// 2. Conditions: Determine the letter grade
switch average {
case 90...100:
    print("Grade: A")
case 80..<90:
    print("Grade: B")
case 70..<80:
    print("Grade: C")
default:
    print("Grade: F (Please see the teacher)")
}

10. Common Mistakes #

• Using = instead of == in if statements: A single = is an assignment operator (giving a box a value). A double == is a comparison operator (checking if two boxes are identical). if name = "Alice" will crash the compiler! It must be if name == "Alice".

• Forgetting the default case in a switch: Swift will rigidly refuse to compile a switch statement if it thinks there is even a 0.01% chance a value might slip through unhandled.

11. Best Practices #

• Switch over If-Else: If you are checking the same variable against 3 or more specific values, always prefer a switch statement over an if / else if chain. It compiles faster and is much easier to read.

12. Exercises #

1. 1. Write an if statement that checks if a variable isBatteryLow is true. If it is, print "Please plug in device".

1. 2. Write a for loop that prints the numbers 10 down to 1. (Hint: Look up reversed() ranges in Swift!).

13. MCQ Quiz with Answers #

14. Interview Questions #

• Q: Explain the mechanical difference between the 1...5 closed range operator and the 1..<5 half-open range operator. In what specific coding scenario is the half-open range critical?

• Q: Contrast a for-in loop with a while loop. Provide a specific architectural scenario where a while loop is the superior choice.

• Q: Describe the concept of an "Infinite Loop". How is it created, and what happens to an iOS application when it occurs on the main thread?

15. Summary #

16. Next Chapter Recommendation #