Comparison operators in Swift - Mini Project: Build & Apply

Comparison Operators in Swift

📖 Scenario: You are helping a small shop owner compare prices of two products to decide which one is cheaper or if they cost the same.

🎯 Goal: Build a simple Swift program that compares two product prices using comparison operators and shows the result.

📋 What You'll Learn

Create two variables with exact prices

Create a variable to hold a comparison threshold

Use comparison operators to compare the prices

Print the comparison result clearly

💡 Why This Matters

🌍 Real World

Comparing prices helps shop owners decide which product to promote or buy.

💼 Career

Understanding comparison operators is essential for decision-making logic in software development.

1

Create price variables

Create two variables called priceA and priceB with values 19.99 and 24.99 respectively.

Swift

# Create two price variables
# Your code here

Hint

Use var to create variables and assign the exact decimal values.

2

Add a price difference threshold

Create a variable called threshold and set it to 0.01 to allow small price differences.

Swift

var priceA = 19.99
var priceB = 24.99
# Create a threshold variable
# Your code here

Hint

This threshold helps to consider prices equal if they differ by less than this amount.

3

Compare the prices using comparison operators

Use if statements with ==, <, and > operators to compare priceA and priceB considering the threshold. Create a variable result that stores the string "Prices are equal", "Price A is cheaper", or "Price B is cheaper" accordingly.

Swift

var priceA = 19.99
var priceB = 24.99
var threshold = 0.01
# Compare prices and set result string
# Your code here

Hint

Use abs() to find the difference and compare with threshold. Assign the correct message to result.

4

Print the comparison result

Print the value of the variable result to show the comparison outcome.

Swift

var priceA = 19.99
var priceB = 24.99
var threshold = 0.01
var result: String
if abs(priceA - priceB) <= threshold {
    result = "Prices are equal"
} else if priceA < priceB {
    result = "Price A is cheaper"
} else {
    result = "Price B is cheaper"
}
# Print the result
# Your code here

Hint

Use print(result) to display the message.

Practice

1. Which of the following comparison operators checks if two values are equal in Swift?

easy

A. ==

B. !=

C. >

D. <=

Solution

1. Step 1: Understand the equality operator

   The operator == is used to check if two values are equal in Swift.

2. Step 2: Compare with other operators

   != means not equal, > means greater than, and <= means less than or equal to.

3. Final Answer:

   == -> Option A

4. Quick Check:

   Equality operator = == [OK]

Hint: Remember: double equals means equality check [OK]

Common Mistakes:

• Confusing == with = (assignment)
• Using != to check equality
• Mixing > and < with equality

2. Which of the following is the correct syntax to check if variable a is not equal to variable b in Swift?

easy

A. a != b

B. a =! b

C. a !== b

D. a <> b

Solution

1. Step 1: Identify the not equal operator in Swift

   Swift uses != to check if two values are not equal.

2. Step 2: Check syntax correctness

   a != b is correct. a =! b is invalid syntax, !== is for identity comparison in some languages but not for value inequality in Swift, and <> is not a Swift operator.

3. Final Answer:

   a != b -> Option A

4. Quick Check:

   Not equal operator = != [OK]

Hint: Not equal always has ! before = [OK]

Common Mistakes:

• Swapping = and ! in != operator
• Using === instead of !=
• Using <> which is not valid in Swift

3. What will be the output of the following Swift code?

let x = 10
let y = 20
print(x > y)

medium

A. true

B. 10

C. 20

D. false

Solution

1. Step 1: Understand the comparison

   The code compares if x (10) is greater than y (20).

2. Step 2: Evaluate the comparison

   Since 10 is not greater than 20, the expression x > y is false.

3. Final Answer:

   false -> Option D

4. Quick Check:

   10 > 20 = false [OK]

Hint: Compare values carefully, > means strictly greater [OK]

Common Mistakes:

• Assuming 10 > 20 is true
• Confusing > with <
• Printing variable values instead of boolean

4. Identify the error in the following Swift code snippet:

let a = 5
let b = 10
if a = b {
    print("Equal")
} else {
    print("Not Equal")
}

medium

A. Using print instead of println

B. Missing parentheses around condition

C. Using = instead of == in if condition

D. Variables a and b must be var, not let

Solution

1. Step 1: Check the if condition syntax

   The condition uses a = b, which is assignment, not comparison.

2. Step 2: Correct operator for comparison

   To compare values, Swift requires == instead of =.

3. Final Answer:

   Using = instead of == in if condition -> Option C

4. Quick Check:

   Comparison needs ==, not = [OK]

Hint: Use == for comparison, = is assignment [OK]

Common Mistakes:

• Using = instead of == in conditions
• Thinking parentheses are mandatory in Swift if
• Confusing print and println functions

5. You want to check if a number n is between 10 and 20 inclusive in Swift. Which of the following expressions correctly uses comparison operators to do this?

hard

A. n > 10 || n < 20

B. n >= 10 && n <= 20

C. n == 10 && n == 20

D. n != 10 && n != 20

Solution

1. Step 1: Understand the range condition

   To check if n is between 10 and 20 inclusive, it must be greater than or equal to 10 and less than or equal to 20.

2. Step 2: Analyze each option

   n >= 10 && n <= 20 uses n >= 10 && n <= 20, which correctly checks the inclusive range. n > 10 || n < 20 uses OR which is incorrect for range. n == 10 && n == 20 checks if n equals both 10 and 20 simultaneously, which is impossible. n != 10 && n != 20 checks if n is not 10 and not 20, which does not ensure the range.

3. Final Answer:

   n >= 10 && n <= 20 -> Option B

4. Quick Check:

   Inclusive range uses >= and <= with AND [OK]

Hint: Use && with >= and <= for inclusive range checks [OK]

Common Mistakes:

• Using || instead of && for range
• Checking equality to both ends at once
• Using != which excludes values instead of range