Why Swift is strongly typed - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a variable with a specific type in Swift.

Swift

var name: [1] = "Alice"

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

AString

Bint

Cfloat

Dboolean

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase types like int or boolean which are not valid in Swift.

In Swift, you declare a variable's type explicitly using String for text values.

2fill in blank

medium

Complete the code to declare a constant integer in Swift.

Swift

let age: [1] = 30

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

ADouble

BString

CInt

DBool

Attempts:

3 left

💡 Hint

Common Mistakes

Using Double or String instead of Int for whole numbers.

Use Int to declare an integer type in Swift.

3fill in blank

hard

Fix the error in the code by specifying the correct type for the variable.

Swift

var isActive: [1] = true

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

Afloat

BString

Cint

DBool

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase or incorrect types like int or float for Boolean values.

The type Bool is used for true/false values in Swift.

4fill in blank

hard

Fill both blanks to create a dictionary with String keys and Int values.

Swift

var scores: [[1]: [2]] = ["Math": 90, "Science": 85]

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

AString

BInt

CDouble

DBool

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up key and value types or using incorrect types like Double or Bool.

Dictionaries in Swift use square brackets with key and value types separated by a colon. Here, keys are String and values are Int.

5fill in blank

hard

Fill all three blanks to create a typed array and access its first element.

Swift

var fruits: [[1]] = ["Apple", "Banana", "Cherry"]
let firstFruit: [2] = fruits[[3]]

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

AString

B0

DInt

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong types for the array or index, or wrong index number.

The array fruits holds String values. The first element is accessed at index 0 and assigned to a variable of type String.

Practice

1. Why does Swift use strong typing for variables and constants?

easy

A. To catch errors early and make code safer

B. To allow variables to change types anytime

C. To make code run faster by ignoring types

D. To let programmers skip declaring types

Solution

1. Step 1: Understand strong typing purpose

   Strong typing means every variable has a fixed type to avoid mistakes.

2. Step 2: Identify why Swift uses it

   Swift uses strong typing to catch errors early and keep code safe.

3. Final Answer:

   To catch errors early and make code safer -> Option A

4. Quick Check:

   Strong typing = safer code [OK]

Hint: Strong typing means fixed types for safety [OK]

Common Mistakes:

• Thinking variables can change types freely
• Believing types are ignored for speed
• Assuming types are optional in Swift

2. Which of the following is the correct way to declare a strongly typed integer variable in Swift?

easy

A. var age = "25"

B. var age: Int = 25

C. var age: String = 25

D. var age = 25.0

Solution

1. Step 1: Check variable declaration syntax

   In Swift, you declare a variable with var, specify type with colon, then assign value.

2. Step 2: Match type and value

   var age: Int = 25 declares age as Int and assigns 25, which is correct for strong typing.

3. Final Answer:

   var age: Int = 25 -> Option B

4. Quick Check:

   Correct type and value match = var age: Int = 25 [OK]

Hint: Match variable type and value exactly [OK]

Common Mistakes:

• Assigning string to an Int type
• Using wrong type annotation
• Mixing number types like Int and Double

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

let number: Int = 10
let text: String = "10"
print(number == Int(text)!)

medium

A. false

B. Compilation error

C. true

D. Runtime error

Solution

1. Step 1: Understand type conversion

   text is a String "10". Int(text)! converts it to Int 10 safely.

2. Step 2: Compare values

   number is Int 10, Int(text)! is also 10, so number == Int(text)! is true.

3. Final Answer:

   true -> Option C

4. Quick Check:

   10 == 10 is true [OK]

Hint: Convert string to Int before comparing [OK]

Common Mistakes:

• Assuming string and int compare directly
• Ignoring forced unwrap with !
• Expecting false because types differ

4. Identify the error in this Swift code snippet:

var score: Int = "100"
print(score)

medium

A. Variable score is not initialized

B. Missing semicolon at end of line

C. print function syntax is incorrect

D. Type mismatch: assigning String to Int variable

Solution

1. Step 1: Check variable type and assigned value

   score is declared as Int but assigned a String "100" which is invalid.

2. Step 2: Understand Swift's strong typing rules

   Swift does not allow assigning a String to an Int variable without conversion.

3. Final Answer:

   Type mismatch: assigning String to Int variable -> Option D

4. Quick Check:

   Type mismatch error = Type mismatch: assigning String to Int variable [OK]

Hint: Match variable type and assigned value exactly [OK]

Common Mistakes:

• Thinking semicolon is required
• Assuming implicit conversion from String to Int
• Believing print syntax is wrong

5. You want to create a function in Swift that accepts only integers and returns their square. Why is strong typing important here?

hard

A. It ensures only integers are passed, preventing errors

B. It allows passing any type without restrictions

C. It automatically converts strings to integers

D. It makes the function run faster by ignoring types

Solution

1. Step 1: Understand function parameter typing

   Strong typing requires the function to accept only Int type, avoiding wrong inputs.

2. Step 2: Recognize benefits of strong typing in functions

   This prevents runtime errors by catching type mistakes early.

3. Final Answer:

   It ensures only integers are passed, preventing errors -> Option A

4. Quick Check:

   Strong typing = safer function inputs [OK]

Hint: Strong typing prevents wrong input types [OK]

Common Mistakes:

• Thinking any type can be passed
• Assuming automatic type conversion
• Believing types slow down functions