Nested structs in Go - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a nested struct field.

Go

type Person struct {
    Name string
    Address [1]
}

type Address struct {
    City string
    Zip  int
}

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

AAddress

Bstring

Cstruct

Dint

Attempts:

3 left

💡 Hint

Common Mistakes

Using basic types like string or int instead of the struct type.

Forgetting to use the struct type name.

The field Address inside Person must be of type Address to nest the struct.

2fill in blank

medium

Complete the code to create a variable of nested struct type.

Go

var p [1]
p = Person{
    Name: "Alice",
    Address: Address{
        City: "Wonderland",
        Zip: 12345,
    },
}

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

AAddress

Bstring

Cstruct

DPerson

Attempts:

3 left

💡 Hint

Common Mistakes

Using the nested struct type Address instead of Person.

Using basic types like string.

The variable p must be of type Person to hold the nested Address struct.

3fill in blank

hard

Fix the error in accessing the nested struct field.

Go

fmt.Println(p.[1].City)

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

AName

BAddress

CZip

DCity

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to access City directly from p.

Using the wrong field name.

To access the city, you must first access the Address field inside p.

4fill in blank

hard

Fill both blanks to define and initialize a nested struct inline.

Go

p := Person{
    Name: "Bob",
    Address: [1]{
        City: "[2]",
        Zip: 54321,
    },
}

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

AAddress

BPerson

CWondercity

DCityville

Attempts:

3 left

💡 Hint

Common Mistakes

Using the outer struct name instead of the nested struct type.

Putting a variable name instead of a string for the city.

The nested struct type is Address, and the city name is a string like Cityville.

5fill in blank

hard

Fill all three blanks to create a nested struct and print a nested field.

Go

type Company struct {
    Name    string
    Founder [1]
}

type Founder struct {
    FirstName string
    LastName  string
}

func main() {
    c := Company{
        Name: "TechCorp",
        Founder: [2]{
            FirstName: "Jane",
            LastName: "Doe",
        },
    }
    fmt.Println(c.Founder.[3])
}

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

AFounder

CFirstName

DLastName

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong struct type or field names.

Trying to print the whole struct instead of a field.

The Founder field in Company is of type Founder. We initialize it with Founder{...} and print the FirstName field.

Practice

1. What is the main purpose of using nested structs in Go?

easy

A. To group related data together inside another struct

B. To create multiple independent structs

C. To make the program run faster

D. To avoid using functions

Solution

1. Step 1: Understand struct grouping

   Nested structs allow one struct to contain another, grouping related data logically.

2. Step 2: Compare options

   Creating multiple independent structs, making the program run faster, or avoiding functions do not describe grouping data inside structs.

3. Final Answer:

   To group related data together inside another struct -> Option A

4. Quick Check:

   Nested structs = Group related data [OK]

Hint: Think of nested structs as folders inside folders [OK]

Common Mistakes:

• Confusing nested structs with separate structs
• Thinking nested structs improve speed
• Believing nested structs replace functions

2. Which of the following is the correct way to access the field City inside a nested struct Address within struct Person?

easy

A. person.City.Address

B. person->Address->City

C. person.Address.City

D. person.Address->City

Solution

1. Step 1: Recall Go syntax for nested structs

   Access nested fields using dot notation: Outer.Inner.Field.

2. Step 2: Evaluate options

   person.Address.City uses correct dot notation. Arrow syntax (->) is invalid in Go. person.City.Address reverses the order.

3. Final Answer:

   person.Address.City -> Option C

4. Quick Check:

   Dot notation = person.Address.City [OK]

Hint: Use dot notation to access nested fields [OK]

Common Mistakes:

• Using arrow (->) instead of dot (.)
• Reversing the order of fields
• Trying to access nested fields directly without parent

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

package main
import "fmt"
type Address struct {
    City string
    Zip  int
}
type Person struct {
    Name    string
    Address Address
}
func main() {
    p := Person{Name: "Anna", Address: Address{City: "Paris", Zip: 75000}}
    fmt.Println(p.Address.City)
}

medium

A. Anna

B. Paris

C. 75000

D. Address

Solution

1. Step 1: Understand struct initialization

   Person struct has Name and Address fields. Address is initialized with City "Paris" and Zip 75000.

2. Step 2: Identify printed field

   The code prints p.Address.City, which is "Paris".

3. Final Answer:

   Paris -> Option B

4. Quick Check:

   p.Address.City = Paris [OK]

Hint: Print nested field with dot notation [OK]

Common Mistakes:

• Printing the wrong field like Name or Zip
• Confusing struct field names
• Expecting the whole struct to print

4. Identify the error in this Go code snippet involving nested structs:

package main
import "fmt"
type Engine struct {
    Power int
}
type Car struct {
    Model  string
    Engine Engine
}
func main() {
    c := Car{Model: "Sedan"}
    fmt.Println(c.Engine.Power)
}

medium

A. c.Engine.Power is zero value, no error

B. Car struct missing Engine field

C. Engine struct is not defined

D. Cannot print nested struct fields directly

Solution

1. Step 1: Check struct definitions

   Engine and Car structs are defined correctly. Car has Engine field.

2. Step 2: Analyze initialization and print

   Car instance c is created with Model only. Engine field is zero-valued (Power = 0). Printing c.Engine.Power prints 0 without error.

3. Final Answer:

   c.Engine.Power is zero value, no error -> Option A

4. Quick Check:

   Uninitialized nested struct fields have zero values [OK]

Hint: Uninitialized nested structs have zero values [OK]

Common Mistakes:

• Assuming missing initialization causes error
• Thinking nested fields can't be printed
• Confusing missing fields with zero values

5. Given the structs below, how would you write a function FullAddress that returns a formatted string combining Street, City, and Zip from nested structs?

type Location struct {
    Street string
    City   string
}
type Address struct {
    Location Location
    Zip      int
}

hard

A. func FullAddress(a Address) string { return a.Street + ", " + a.City + " " + fmt.Sprint(a.Zip) }

B. func FullAddress(a Address) string { return a.Street + ", " + a.Location.City + " " + fmt.Sprint(a.Zip) }

C. func FullAddress(a Address) string { return a.Location.Street + ", " + a.City + " " + fmt.Sprint(a.Zip) }

D. func FullAddress(a Address) string { return a.Location.Street + ", " + a.Location.City + " " + fmt.Sprint(a.Zip) }

Solution

1. Step 1: Identify nested fields

   Street and City are inside Location struct, which is nested inside Address.

2. Step 2: Access nested fields correctly

   Use a.Location.Street and a.Location.City to access those fields, and a.Zip for Zip code.

3. Step 3: Check options

   Only func FullAddress(a Address) string { return a.Location.Street + ", " + a.Location.City + " " + fmt.Sprint(a.Zip) } correctly accesses nested fields with dot notation.

4. Final Answer:

   func FullAddress(a Address) string { return a.Location.Street + ", " + a.Location.City + " " + fmt.Sprint(a.Zip) } -> Option D

5. Quick Check:

   Access nested fields with dot notation [OK]

Hint: Use dot notation for each nested level [OK]

Common Mistakes:

• Accessing nested fields directly without parent struct
• Mixing field names from different structs
• Forgetting to convert int Zip to string