Nested structs in Go - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of nested struct field access

What is the output of this Go program?

Go

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

A 75000

B Address{City: "Paris", Zip: 75000}

C Alice

D Paris

💡 Hint

Look at how nested structs are accessed using dot notation.

The field City is inside the nested Address struct. Accessing p.Address.City prints "Paris".

❓ Predict Output

intermediate

Output of nested struct pointer access

What will this Go program print?

Go

package main
import "fmt"
type Engine struct {
    Horsepower int
}
type Car struct {
    Model  string
    Engine *Engine
}
func main() {
    e := Engine{Horsepower: 300}
    c := Car{Model: "Mustang", Engine: &e}
    fmt.Println(c.Engine.Horsepower)
}

A Mustang

B nil

C 300

D 0

💡 Hint

Remember to dereference pointers automatically with dot notation.

The Engine field is a pointer to Engine struct. Accessing c.Engine.Horsepower prints 300.

🔧 Debug

advanced

Identify the compilation error in nested struct initialization

This Go code does not compile. What is the cause of the error?

Go

package main
import "fmt"
type Point struct {
    X, Y int
}
type Rectangle struct {
    TopLeft, BottomRight Point
}
func main() {
    r := Rectangle{TopLeft: Point{X: 0, Y: 10}, BottomRight: Point{X: 5, Y: 0}}
    fmt.Println(r)
}

A Missing type name in nested struct literals

B Cannot use composite literals inside struct initialization

C Fields TopLeft and BottomRight are unexported

D fmt.Println cannot print structs

💡 Hint

Check how nested structs are initialized in Go.

In Go, nested struct literals must include the type name. Using {X:0, Y:10} alone causes a syntax error.

❓ Predict Output

advanced

Output of embedded struct field promotion

What does this Go program print?

Go

package main
import "fmt"
type Contact struct {
    Email string
}
type Employee struct {
    Name    string
    Contact
}
func main() {
    e := Employee{Name: "Bob", Contact: Contact{Email: "[e-mail]"}}
    fmt.Println(e.Email)
}

A Name field value: Bob

B [e-mail]

C Compilation error: ambiguous field

D Contact{Email: "[e-mail]"}

💡 Hint

Embedded structs promote their fields to the outer struct.

The embedded Contact struct's Email field is promoted, so e.Email accesses it directly.

🧠 Conceptual

expert

Number of fields in nested and embedded structs

Given these struct definitions, how many fields does variable 'd' of type Developer have?

Go

type Address struct {
    City string
    Zip  int
}
type Contact struct {
    Email string
    Phone string
}
type Developer struct {
    Name    string
    Address
    Contact
}

A 5

B 3

C 4

D 6

💡 Hint

Count all fields including embedded struct fields promoted to Developer.

Developer has Name plus all fields from Address (City, Zip) and Contact (Email, Phone), total 5 fields.