Logical operators in Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to check if both conditions are true.

Swift

let isSunny = true
let isWarm = true
if isSunny [1] isWarm {
    print("Let's go outside!")
}

Drag options to blanks, or click blank then click option'

A==

B||

C!

D&&

Attempts:

3 left

💡 Hint

Common Mistakes

Using || instead of && causes the condition to be true if either is true.

The && operator checks if both conditions are true.

2fill in blank

medium

Complete the code to check if at least one condition is true.

Swift

let hasUmbrella = false
let isRaining = true
if hasUmbrella [1] isRaining {
    print("You can go outside.")
}

Drag options to blanks, or click blank then click option'

A||

B&&

C!=

D==

Attempts:

3 left

💡 Hint

Common Mistakes

Using && instead of || requires both conditions to be true.

The || operator means 'or' and returns true if at least one condition is true.

3fill in blank

hard

Fix the error in the code to negate the condition correctly.

Swift

let isWeekend = false
if [1]isWeekend {
    print("Time to relax!")
}

Drag options to blanks, or click blank then click option'

A!

B&&

C||

D==

Attempts:

3 left

💡 Hint

Common Mistakes

Using == instead of ! does not negate the value.

The ! operator negates the Boolean value, making false become true.

4fill in blank

hard

Fill both blanks to check if the number is between 10 and 20 (inclusive).

Swift

let number = 15
if number [1] 10 [2] number <= 20 {
    print("Number is between 10 and 20.")
}

Drag options to blanks, or click blank then click option'

A>=

B<

C&&

D||

Attempts:

3 left

💡 Hint

Common Mistakes

Using || instead of && allows numbers outside the range.

Use >= to check if number is at least 10, and && to combine conditions.

5fill in blank

hard

Fill all three blanks to check if a character is a vowel (a, e, i, o, u).

Swift

let char: Character = 'e'
if char == 'a' [1] char == 'e' [2] char == 'i' [3] char == 'o' || char == 'u' {
    print("It's a vowel.")
}

Drag options to blanks, or click blank then click option'

A||

B&&

Attempts:

3 left

💡 Hint

Common Mistakes

Using && requires all conditions to be true, which is impossible here.

Use || to check if the character matches any vowel.

Practice

1. Which logical operator in Swift returns true only if both conditions are true?

easy

A. == (Equality)

B. || (OR)

C. && (AND)

D. ! (NOT)

Solution

1. Step 1: Understand the AND operator

   The AND operator (&&) returns true only when both conditions it connects are true.

2. Step 2: Compare with other operators

   The OR operator (||) returns true if at least one condition is true, NOT (!) flips true to false and vice versa, and == checks equality, not logical combination.

3. Final Answer:

   && (AND) -> Option C

4. Quick Check:

   AND = && [OK]

Hint: AND needs both true; look for && operator [OK]

Common Mistakes:

• Confusing AND (&&) with OR (||)
• Thinking NOT (!) combines conditions
• Mixing equality (==) with logical operators

2. Which of the following is the correct syntax to negate a Boolean value isActive in Swift?

easy

A. !isActive

B. not isActive

C. isActive!

D. isActive.not()

Solution

1. Step 1: Recall the NOT operator syntax

   In Swift, the NOT operator is written as an exclamation mark (!) placed before the Boolean variable to flip its value.

2. Step 2: Check each option

   !isActive is the correct syntax. The other options are not valid Swift syntax for negation.

3. Final Answer:

   !isActive -> Option A

4. Quick Check:

   NOT = ! before variable [OK]

Hint: Use ! before variable to negate Boolean [OK]

Common Mistakes:

• Writing 'not' instead of '!'
• Putting ! after variable name
• Using method calls like .not()

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

let a = true
let b = false
print(a || b && !b)

medium

A. Syntax Error

B. true

C. false

D. nil

Solution

1. Step 1: Evaluate the NOT operator

   !b means !false which is true.

2. Step 2: Evaluate AND operator

   b && !b is false && true which is false.

3. Step 3: Evaluate OR operator

   a || (result of AND) is true || false which is true.

4. Final Answer:

   true -> Option B

5. Quick Check:

   OR with true = true [OK]

Hint: Remember NOT first, then AND, then OR [OK]

Common Mistakes:

• Ignoring operator precedence
• Evaluating OR before AND
• Misunderstanding ! operator

4. Identify the error in this Swift code snippet:

let x = true
let y = false
if x || && y {
    print("Yes")
}

medium

A. Missing parentheses around conditions

B. print statement syntax error

C. Variables x and y are not Boolean

D. Incorrect use of logical operators together

Solution

1. Step 1: Analyze the if condition syntax

   The condition uses 'x || && y' which combines OR (||) and AND (&&) operators without a proper operand between them.

2. Step 2: Identify the logical operator misuse

   Logical operators must connect two Boolean expressions. Here, '|| &&' is invalid syntax.

3. Final Answer:

   Incorrect use of logical operators together -> Option D

4. Quick Check:

   Operators must connect expressions properly [OK]

Hint: Operators need operands on both sides [OK]

Common Mistakes:

• Writing two operators without a condition between
• Assuming parentheses fix operator misuse
• Confusing variable types with operator errors

5. You want to check if a number n is between 10 and 20 inclusive in Swift. Which condition correctly uses logical operators?

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, n must be greater than or equal to 10 AND less than or equal to 20.

2. Step 2: Evaluate each option

   n >= 10 || n <= 20 uses OR which is incorrect because it allows values outside the range. n > 10 && n < 20 excludes 10 and 20 by using > and <. !(n < 10 && n > 20) negates an impossible condition and is incorrect.

3. Final Answer:

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

4. Quick Check:

   Use AND for range checks [OK]

Hint: Use && to combine lower and upper bounds [OK]

Common Mistakes:

• Using OR instead of AND for range
• Excluding boundary values by using > or <
• Using negation incorrectly for range