If and if-else statements in Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to check if the number is positive.

Swift

let number = 5
if number [1] 0 {
    print("Positive number")
}

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

A==

B>

C<

D!=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' instead of '>' will check for negative numbers.

The condition number > 0 checks if the number is positive.

2fill in blank

medium

Complete the code to print "Even" if the number is divisible by 2.

Swift

let number = 8
if number % 2 [1] 0 {
    print("Even")
}

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

A!=

B<

C>

D==

Attempts:

3 left

💡 Hint

Common Mistakes

Using '!=' will check for odd numbers instead.

The condition number % 2 == 0 checks if the number is even.

3fill in blank

hard

Fix the error in the if-else statement to print "Adult" if age is 18 or more.

Swift

let age = 20
if age [1] 18 {
    print("Adult")
} else {
    print("Minor")
}

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

A>=

B<

C==

D!=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' will check for ages less than 18, which is incorrect here.

The condition age >= 18 correctly checks if age is 18 or older.

4fill in blank

hard

Fill both blanks to print "Child" if age is less than 13, otherwise "Teen or Adult".

Swift

let age = 10
if age [1] 13 {
    print("Child")
} [2] {
    print("Teen or Adult")
}

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

A<

B>

Celse

Delif

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'elif' instead of 'else' in the second blank causes syntax error.

The first blank uses '<' to check if age is less than 13. The second blank is the keyword else for the alternative case.

5fill in blank

hard

Fill all three blanks to print "Positive", "Negative", or "Zero" based on the value of number.

Swift

let number = 0
if number [1] 0 {
    print("Positive")
} else if number [2] 0 {
    print("Negative")
} [3] {
    print("Zero")
}

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

A>

B<

Celse

D==

Attempts:

3 left

💡 Hint

Common Mistakes

Using '==' in the first or second blank causes wrong logic.

The first blank checks if number is greater than zero. The second blank checks if number is less than zero. The third blank is the else keyword for zero.

Practice

1. What does an if statement do in Swift?

easy

A. It runs code only if a condition is true.

B. It repeats code multiple times.

C. It stores data in a variable.

D. It defines a new function.

Solution

1. Step 1: Understand the purpose of if statement

   An if statement checks a condition and runs code only when that condition is true.

2. Step 2: Compare with other options

   Repeating code is done by loops, storing data is done by variables, and defining functions uses func.

3. Final Answer:

   It runs code only if a condition is true. -> Option A

4. Quick Check:

   If statement = runs code if true [OK]

Hint: If checks true condition to run code, else skips it [OK]

Common Mistakes:

• Confusing if with loops
• Thinking if stores data
• Mixing if with function definitions

2. Which of the following is the correct syntax for an if-else statement in Swift?

easy

A. if condition { } else { }

B. if (condition) then { } else { }

C. if condition then { } else { }

D. if condition: { } else: { }

Solution

1. Step 1: Recall Swift if-else syntax

   Swift uses if condition { } and else { } blocks without extra keywords like 'then' or colons.

2. Step 2: Check each option

   if condition { } else { } matches Swift syntax exactly. Options A, B, and C use invalid keywords or punctuation.

3. Final Answer:

   if condition { } else { } -> Option A

4. Quick Check:

   Swift if-else = if condition { } else { } [OK]

Hint: Swift uses braces {} without 'then' or colons in if-else [OK]

Common Mistakes:

• Adding 'then' keyword
• Using colons after if or else
• Putting condition in parentheses unnecessarily

3. What will be printed by this Swift code?

let number = 10
if number > 5 {
    print("Big")
} else {
    print("Small")
}

medium

A. Small

B. No output

C. 10

D. Big

Solution

1. Step 1: Evaluate the condition

   The variable number is 10. The condition number > 5 is true because 10 is greater than 5.

2. Step 2: Determine which block runs

   Since the condition is true, the code inside the if block runs, printing "Big".

3. Final Answer:

   Big -> Option D

4. Quick Check:

   10 > 5 is true, so prints "Big" [OK]

Hint: Check condition true? Run if block, else run else block [OK]

Common Mistakes:

• Confusing which block runs
• Printing variable instead of string
• Ignoring condition result

4. Find the error in this Swift code:

let age = 18
if age >= 18
    print("Adult")
else
    print("Minor")

medium

A. Variable age should be a string

B. Wrong comparison operator

C. Missing braces { } around if and else blocks

D. No error, code is correct

Solution

1. Step 1: Check Swift if-else syntax

   Swift requires braces { } around the code blocks after if and else.

2. Step 2: Identify missing braces

   The code lacks braces after if age >= 18 and else, causing a syntax error.

3. Final Answer:

   Missing braces { } around if and else blocks -> Option C

4. Quick Check:

   Swift needs braces for if-else blocks [OK]

Hint: Always use { } after if and else in Swift [OK]

Common Mistakes:

• Omitting braces in if-else
• Using wrong operators
• Wrong variable types

5. You want to write Swift code that prints "Positive", "Negative", or "Zero" depending on the value of an integer variable num. Which code correctly uses if-else statements to do this?

hard

A. if num >= 0 {
print("Positive")
} else if num <= 0 {
print("Negative")
} else {
print("Zero")
}

B. if num > 0 {
print("Positive")
} else if num < 0 {
print("Negative")
} else {
print("Zero")
}

C. if num > 0 {
print("Positive")
} else {
print("Negative")
}
print("Zero")

D. if num == 0 {
print("Zero")
} else if num > 0 {
print("Negative")
} else if num < 0 {
print("Positive")
}

Solution

1. Step 1: Understand the conditions needed

   We need to check if num is greater than 0, less than 0, or exactly 0.

2. Step 2: Analyze each option

   if num > 0 { print("Positive") } else if num < 0 { print("Negative") } else { print("Zero") } correctly checks >0, then <0, else zero. if num >= 0 { print("Positive") } else if num <= 0 { print("Negative") } else { print("Zero") } wrongly overlaps conditions. if num > 0 { print("Positive") } else { print("Negative") } print("Zero") prints "Zero" always. if num == 0 { print("Zero") } else if num > 0 { print("Negative") } else if num < 0 { print("Positive") } incorrectly prints "Negative" for positive numbers and "Positive" for negative numbers.

3. Final Answer:

   if num > 0 { print("Positive") } else if num < 0 { print("Negative") } else { print("Zero") } -> Option B

4. Quick Check:

   Check >0, else if <0, else zero [OK]

Hint: Check positive first, then negative, else zero last [OK]

Common Mistakes:

• Overlapping conditions causing wrong output
• Printing zero outside else block
• Wrong order of conditions