String interpolation in Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to print the value of the variable inside the string.

Swift

let name = "Alice"
print("Hello, \([1])!")

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

A"name"

Bname()

Cname

DName

Attempts:

3 left

💡 Hint

Common Mistakes

Putting the variable name in quotes inside the interpolation.

Using parentheses after the variable name like a function call.

In Swift, to insert a variable's value inside a string, use \(variableName). Here, \(name) inserts the value of 'name'.

2fill in blank

medium

Complete the code to include the sum of two numbers inside the string.

Swift

let a = 5
let b = 3
print("Sum is \([1])")

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

Aa + b

B"a + b"

Csum(a, b)

Da.plus(b)

Attempts:

3 left

💡 Hint

Common Mistakes

Putting the expression inside quotes, which prints the expression as text.

Using a function that doesn't exist like sum(a, b).

Inside string interpolation, you can write expressions like 'a + b' to calculate and insert the result.

3fill in blank

hard

Fix the error in the string interpolation to correctly show the age.

Swift

let age = 30
print("Age: [1]")

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

A(age)

Bage

C"age"

D\(age)

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting the \( ) around the variable.

Putting the variable name in quotes.

To insert a variable's value inside a string in Swift, you must use \(variable). Just writing 'age' will print the word, not the value.

4fill in blank

hard

Fill both blanks to create a string that shows the temperature with a degree symbol.

Swift

let temp = 22
let unit = "C"
let message = "Temperature: \([1])\([2])°"

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

Atemp

Bunit

Ctemp + unit

D"temp"

Attempts:

3 left

💡 Hint

Common Mistakes

Putting variables in quotes inside interpolation.

Trying to combine variables inside one interpolation.

Use \(temp) and \(unit) to insert the temperature value and unit inside the string.

5fill in blank

hard

Fill all three blanks to create a greeting with name, age, and city using string interpolation.

Swift

let name = "Bob"
let age = 25
let city = "Paris"
let greeting = "Hi, I am [1], [2] years old, from [3]."

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

A\(name)

B\(age)

C\(city)

Dname

Attempts:

3 left

💡 Hint

Common Mistakes

Using variable names without \( ) inside the string.

Putting variable names in quotes.

Each blank must have the variable inside \( ) to insert its value into the string.

Practice

1. What does string interpolation in Swift allow you to do?

easy

A. Convert a string to uppercase or lowercase

B. Create a new string by repeating characters multiple times

C. Split a string into an array of characters

D. Insert variables or expressions directly inside a string using \( )

Solution

1. Step 1: Understand string interpolation purpose

   String interpolation lets you put variables or expressions inside a string easily.

2. Step 2: Recognize the syntax

   Using \( ) inside double quotes inserts the value dynamically.

3. Final Answer:

   Insert variables or expressions directly inside a string using \( ) -> Option D

4. Quick Check:

   String interpolation = Insert variables with \( ) [OK]

Hint: Remember: \( ) inside quotes inserts values fast [OK]

Common Mistakes:

• Confusing interpolation with string repetition
• Trying to use single quotes instead of double quotes
• Forgetting the backslash before parentheses

2. Which of the following is the correct way to use string interpolation in Swift to show the value of variable score inside a string?

easy

A. "Your score is: ${score}"

B. "Your score is: score"

C. "Your score is: \(score)"

D. "Your score is: {score}"

Solution

1. Step 1: Identify correct interpolation syntax

   Swift uses \(variable) inside double quotes for interpolation.

2. Step 2: Check each option

   "Your score is: \(score)" uses \(score), which is correct. Others use wrong syntax.

3. Final Answer:

   "Your score is: \(score)" -> Option C

4. Quick Check:

   Swift interpolation = \(variable) [OK]

Hint: Use backslash and parentheses for variables inside strings [OK]

Common Mistakes:

• Using ${} like in other languages
• Forgetting the backslash before parentheses
• Not using double quotes around the string

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

let name = "Anna"
let age = 30
print("\(name) is \(age) years old.")

medium

A. Anna is 30 years old.

B. name is age years old.

C. \(name) is \(age) years old.

D. Anna is \(age) years old.

Solution

1. Step 1: Understand variable values

   name = "Anna", age = 30.

2. Step 2: Apply string interpolation

   "\(name)" becomes "Anna", "\(age)" becomes "30" in the string.

3. Final Answer:

   Anna is 30 years old. -> Option A

4. Quick Check:

   Interpolation replaces variables with values [OK]

Hint: Replace \(variable) with its value inside the string [OK]

Common Mistakes:

• Printing the literal \(name) instead of value
• Confusing variable names with strings
• Missing backslash causing no interpolation

4. Identify the error in this Swift code snippet using string interpolation:

let temperature = 22
print("The temperature is (temperature) degrees.")

medium

A. Missing backslash before parentheses in interpolation

B. Variable temperature is not declared

C. Using single quotes instead of double quotes

D. Parentheses should be square brackets

Solution

1. Step 1: Check interpolation syntax

   Interpolation requires a backslash before parentheses: \(variable).

2. Step 2: Identify missing backslash

   Code uses (temperature) without backslash, so it won't interpolate.

3. Final Answer:

   Missing backslash before parentheses in interpolation -> Option A

4. Quick Check:

   Backslash is required for interpolation [OK]

Hint: Always add \ before (variable) in strings [OK]

Common Mistakes:

• Forgetting the backslash
• Using wrong quote types
• Assuming parentheses alone interpolate

5. You want to create a message that shows the total price including tax. Given price = 50 and taxRate = 0.1, which Swift code correctly uses string interpolation to print "Total price: 55.0"?

hard

A. print("Total price: \(price + taxRate)")

B. print("Total price: \(price * (1 + taxRate))")

C. print("Total price: \(price * taxRate)")

D. print("Total price: \(price + taxRate * 100)")

Solution

1. Step 1: Calculate total price with tax

   Total price = price * (1 + taxRate) = 50 * 1.1 = 55.0.

2. Step 2: Check each option's expression

   print("Total price: \(price * (1 + taxRate))"): print("Total price: \(price * (1 + taxRate))") = 55.0 correct. A: \(price + taxRate) = 50.1 wrong. C: \(price * taxRate) = 5.0 (tax only) wrong. D: \(price + taxRate * 100) = 60 wrong.

3. Final Answer:

   print("Total price: \(price * (1 + taxRate))") -> Option B

4. Quick Check:

   Use price * (1 + taxRate) for total [OK]

Hint: Multiply price by (1 + taxRate) inside \( ) [OK]

Common Mistakes:

• Adding taxRate directly instead of multiplying
• Forgetting parentheses around (1 + taxRate)
• Multiplying taxRate by 100 incorrectly