Switch with where clauses in Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to match the number 10 in the switch statement.

Swift

let number = 10
switch number {
case  [1]:
    print("Number is ten")
default:
    print("Number is something else")
}

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

A5

B15

C20

D10

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing a number different from 10 will not match the case.

The case must match the value 10 to print "Number is ten".

2fill in blank

medium

Complete the where clause to check if the number is even.

Swift

let number = 8
switch number {
case let x where x [1] 2 == 0:
    print("Even number")
default:
    print("Odd number")
}

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

A-

B+

C%

D*

Attempts:

3 left

💡 Hint

Common Mistakes

Using + or - instead of % will not check evenness.

The modulo operator (%) checks the remainder. If remainder is 0 when divided by 2, the number is even.

3fill in blank

hard

Fix the error in the where clause to check if the number is positive.

Swift

let number = -3
switch number {
case let x where x [1] 0:
    print("Positive number")
default:
    print("Non-positive number")
}

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

A<

B>

C==

D!=

Attempts:

3 left

💡 Hint

Common Mistakes

Using < will check for negative numbers instead.

To check if a number is positive, it must be greater than 0.

4fill in blank

hard

Fill both blanks to check if the number is between 1 and 10 inclusive.

Swift

let number = 7
switch number {
case let x where x [1] 1 && x [2] 10:
    print("Number is between 1 and 10")
default:
    print("Number is out of range")
}

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

A>=

B<

C<=

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Using > or < only excludes the boundary numbers.

The number should be greater than or equal to 1 and less than or equal to 10.

5fill in blank

hard

Fill both blanks to check if the number is odd and greater than 5.

Swift

let number = 7
switch number {
case let x where x [1] 2 != 0 && x [2] 5:
    print("Odd number greater than 5")
default:
    print("Other number")
}

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

A%

B>

C==

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using == 0 checks even numbers, not odd.

The modulo operator % checks oddness (not equal to 0), and > 5 checks if number is greater than 5.

Practice

1.

What does a where clause do in a Swift switch statement?

easy

A. It defines the default case in the switch statement.

B. It adds an extra condition to a case to check before matching.

C. It repeats the case multiple times automatically.

D. It changes the type of the value being switched.

Solution

1. Step 1: Understand the role of where clause

   The where clause adds an extra condition to a case in a switch statement.

2. Step 2: Compare with other options

   Other options describe unrelated behaviors like default case or type changes, which are not what where does.

3. Final Answer:

   It adds an extra condition to a case to check before matching. -> Option B

4. Quick Check:

   where clause = extra condition [OK]

Hint: Remember: where adds conditions to cases [OK]

Common Mistakes:

• Thinking where defines default case
• Confusing where with case repetition
• Assuming where changes variable types

2.

Which of the following is the correct syntax for a switch case with a where clause in Swift?

let number = 10
switch number {
    case let x where x > 5:
        print("Greater than 5")
    default:
        print("5 or less")
}

easy

A. case let x if x > 5:

B. case x where x > 5:

C. case let x where x > 5:

D. case x if x > 5:

Solution

1. Step 1: Identify correct pattern binding syntax

   In Swift, to bind a value in a case, use let x before the where clause.

2. Step 2: Check the where clause usage

   The where clause follows the pattern binding, so case let x where x > 5: is correct.

3. Final Answer:

   case let x where x > 5: -> Option C

4. Quick Check:

   Pattern binding with let + where clause = case let x where x > 5: [OK]

Hint: Use 'let' before variable, then 'where' for condition [OK]

Common Mistakes:

• Omitting 'let' before variable
• Using 'if' instead of 'where'
• Placing 'where' before 'let'

3.

What will be printed by this Swift code?

let age = 20
switch age {
case let x where x < 13:
    print("Child")
case let x where x >= 13 && x < 20:
    print("Teenager")
case let x where x >= 20:
    print("Adult")
default:
    print("Unknown")
}

medium

A. Adult

B. Teenager

C. Child

D. Unknown

Solution

1. Step 1: Check the value of age

   The variable age is 20.

2. Step 2: Evaluate each case condition

   First case: x < 13? No (20 < 13 is false). Second case: 13 <= x < 20? No (20 < 20 is false). Third case: x >= 20? Yes (20 >= 20 is true).

3. Final Answer:

   Adult -> Option A

4. Quick Check:

   age 20 matches 'Adult' case [OK]

Hint: Check conditions in order; first true case runs [OK]

Common Mistakes:

• Choosing 'Teenager' because 20 is close to 19
• Ignoring >= and < operators
• Forgetting switch stops at first match

4.

Identify the error in this Swift switch statement using where clauses:

let score = 85
switch score {
case let x where x > 90:
    print("Excellent")
case let x where x >= 80:
    print("Good")
case let x where x >= 70:
    print("Average")
case _:
    print("Poor")
}

medium

A. Using let binding is not allowed with where.

B. Missing default case for unmatched values.

C. Incorrect syntax for where clause.

D. The cases overlap and order causes wrong matching.

Solution

1. Step 1: Analyze case conditions and order

   The cases check if score > 90, then >= 80, then >= 70. Since 85 >= 80 and also >= 70, the second case matches first.

2. Step 2: Understand overlapping conditions effect

   Because cases overlap, order matters. If order was different, output might change. This can cause confusion or wrong matching.

3. Final Answer:

   The cases overlap and order causes wrong matching. -> Option D

4. Quick Check:

   Overlapping where clauses need careful order [OK]

Hint: Order cases from most specific to least specific [OK]

Common Mistakes:

• Ignoring overlapping conditions
• Assuming default case is mandatory
• Thinking let binding disallowed with where

5.

You want to categorize a number as "Small", "Medium", or "Large" using a switch with where clauses. The rules are:

• Small: less than 10
• Medium: between 10 and 100 inclusive
• Large: greater than 100

Which switch statement correctly implements this?

let value = 50
switch value {
    case let x where x < 10:
        print("Small")
    case let x where x >= 10 && x <= 100:
        print("Medium")
    case let x where x > 100:
        print("Large")
    default:
        print("Unknown")
}

hard

A. Correctly categorizes all values as per rules.

B. Fails to categorize values equal to 10 or 100.

C. Has syntax errors in where clauses.

D. Default case will never be reached.

Solution

1. Step 1: Check each case condition against rules

   First case: x < 10 matches "Small". Second case: x >= 10 and x <= 100 matches "Medium". Third case: x > 100 matches "Large".

2. Step 2: Verify coverage and syntax

   All values fit one of these cases. Syntax is correct with let x where clauses. Default is fallback but not needed here.

3. Final Answer:

   Correctly categorizes all values as per rules. -> Option A

4. Quick Check:

   Conditions cover all ranges correctly [OK]

Hint: Use clear, non-overlapping where conditions [OK]

Common Mistakes:

• Overlapping ranges causing wrong matches
• Missing <= or >= in conditions
• Forgetting to bind variable with let