Struct declaration syntax in Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a struct named Person.

Swift

struct [1] {
    var name: String
}

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

Aperson

Bfunc

Cclass

DPerson

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase for struct name.

Using keywords like class or func instead of a name.

The keyword struct is followed by the struct name, which should start with a capital letter by convention. Here, Person is the correct struct name.

2fill in blank

medium

Complete the code to add an integer property called age to the struct.

Swift

struct Person {
    var name: String
    var [1]: Int
}

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

Aage

BAge

Cnumber

Dyears

Attempts:

3 left

💡 Hint

Common Mistakes

Using uppercase for property name.

Using unrelated names like years or number.

The property name should be age in lowercase to follow Swift naming conventions.

3fill in blank

hard

Fix the error in the struct declaration by completing the missing keyword.

Swift

[1] Person {
    var name: String
    var age: Int
}

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

Aclass

Bstruct

Cfunc

Dvar

Attempts:

3 left

💡 Hint

Common Mistakes

Using class instead of struct.

Omitting the keyword entirely.

The keyword struct is required to declare a struct in Swift.

4fill in blank

hard

Fill both blanks to declare a struct with a method that returns a greeting.

Swift

struct Person {
    var name: String
    func [1]() -> String {
        return "Hello, \(self.[2])!"
    }
}

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

Agreet

Bname

CsayHello

Dage

Attempts:

3 left

💡 Hint

Common Mistakes

Using a method name that doesn't match the greeting purpose.

Referencing a property that doesn't exist.

The method name is greet and it uses the property name to return a greeting.

5fill in blank

hard

Fill all three blanks to declare a struct with a computed property that returns a description.

Swift

struct Person {
    var name: String
    var age: Int
    var [1]: String {
        return "\(self.[2]) is \(self.[3]) years old."
    }
}

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

Adescription

Bname

Cage

Dgreeting

Attempts:

3 left

💡 Hint

Common Mistakes

Using a wrong property name for the computed property.

Mixing up property names inside the string.

The computed property is named description and it returns a string using the name and age properties.

Practice

1. What keyword is used to declare a struct in Swift?

easy

A. struct

B. class

C. function

D. var

Solution

1. Step 1: Identify the keyword for struct declaration

   In Swift, the keyword struct is used to declare a struct type.

2. Step 2: Differentiate from other keywords

   class declares classes, function is not a Swift keyword, and var declares variables.

3. Final Answer:

   struct -> Option A

4. Quick Check:

   Keyword for struct declaration = struct [OK]

Hint: Remember: struct keyword starts struct declarations [OK]

Common Mistakes:

• Using class instead of struct
• Confusing var with struct
• Trying function keyword
• Omitting the keyword

2. Which of the following is the correct syntax to declare a struct named Person with a property name of type String?

easy

A. struct Person = { var name: String }

B. struct Person (var name: String)

C. struct Person { var name: String }

D. struct Person: var name String

Solution

1. Step 1: Check struct declaration syntax

   Structs use curly braces {} to enclose properties. Properties are declared with var or let inside braces.

2. Step 2: Validate each option

   struct Person { var name: String } uses correct syntax: struct Person { var name: String }. Others misuse parentheses, equal sign, or colons incorrectly.

3. Final Answer:

   struct Person { var name: String } -> Option C

4. Quick Check:

   Struct syntax uses braces and var for properties [OK]

Hint: Use braces {} and var for properties inside struct [OK]

Common Mistakes:

• Using parentheses instead of braces
• Adding equal sign after struct name
• Incorrect colon usage
• Missing var keyword

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

struct Car {
    var model: String
    func description() -> String {
        return "Car model is \(model)"
    }
}
let myCar = Car(model: "Tesla")
print(myCar.description())

medium

A. Car model is Tesla

B. Car model is model

C. Tesla

D. Error: Missing initializer

Solution

1. Step 1: Understand struct with property and method

   The struct Car has a property model and a method description() that returns a string including the model.

2. Step 2: Analyze code execution

   Creating myCar with model "Tesla" and calling description() returns "Car model is Tesla" which is printed.

3. Final Answer:

   Car model is Tesla -> Option A

4. Quick Check:

   Method returns string with model value [OK]

Hint: Methods can use properties with \(property) inside strings [OK]

Common Mistakes:

• Expecting property name printed literally
• Forgetting to call method
• Assuming error due to no explicit initializer
• Confusing output with just model string

4. Identify the error in this struct declaration:

struct Book {
    var title String
    var pages: Int
}

medium

A. Missing var keyword before pages

B. Curly braces missing

C. Struct keyword misspelled

D. Missing colon after title

Solution

1. Step 1: Check property declarations

   Each property must have a colon between name and type, e.g., var title: String.

2. Step 2: Identify the error

   The line var title String is missing the colon after title. Other parts are correct.

3. Final Answer:

   Missing colon after title -> Option D

4. Quick Check:

   Property syntax requires colon between name and type [OK]

Hint: Always put colon between property name and type [OK]

Common Mistakes:

• Omitting colon between name and type
• Forgetting var keyword
• Misspelling struct
• Missing braces

5. You want to create a struct Rectangle with properties width and height (both Int), and a method area() that returns the area as Int. Which is the correct complete declaration?

hard

A. struct Rectangle {
var width Int
var height Int
func area() -> Int {
return width + height
}
}

B. struct Rectangle {
var width: Int
var height: Int
func area() -> Int {
return width * height
}
}

C. struct Rectangle {
var width: Int
var height: Int
func area() {
width * height
}
}

D. struct Rectangle {
width: Int
height: Int
func area() -> Int {
return width * height
}
}

Solution

1. Step 1: Check property declarations

   Properties must have var keyword and colon between name and type. struct Rectangle { var width: Int var height: Int func area() -> Int { return width * height } } correctly uses var width: Int and var height: Int.

2. Step 2: Check method syntax and logic

   Method area() returns Int and correctly calculates width * height. struct Rectangle { var width: Int var height: Int func area() -> Int { return width * height } } matches this.

3. Final Answer:

   Complete struct with correct properties and method -> Option B

4. Quick Check:

   Properties need var and colon; method returns correct calculation [OK]

Hint: Use var with colon for properties; return correct calculation [OK]

Common Mistakes:

• Omitting var keyword
• Missing colon after property name
• Method missing return type
• Incorrect calculation in method