Defining structs in Go - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of struct field access

What is the output of this Go program?

Go

package main
import "fmt"
type Person struct {
  Name string
  Age  int
}
func main() {
  p := Person{Name: "Alice", Age: 30}
  fmt.Println(p.Name)
}

A Alice

B 30

C Person{Name: "Alice", Age: 30}

D Compilation error

💡 Hint

Look at which field is printed with fmt.Println.

The program creates a Person struct with Name "Alice" and Age 30. It prints p.Name, so output is "Alice".

❓ Predict Output

intermediate

Output when struct fields are uninitialized

What is the output of this Go program?

Go

package main
import "fmt"
type Point struct {
  X int
  Y int
}
func main() {
  var p Point
  fmt.Println(p.X, p.Y)
}

A nil nil

B Compilation error: missing initialization

C 0 0

D Random values

💡 Hint

Uninitialized int fields default to zero.

In Go, int fields default to 0 if not initialized. So p.X and p.Y print as 0 0.

🔧 Debug

advanced

Identify the error in struct initialization

What error does this Go code produce?

Go

package main
import "fmt"
type Car struct {
  Brand string
  Year  int
}
func main() {
  c := Car{Brand: "Toyota", Year: 2020}
  fmt.Println(c)
}

A Syntax error: mixed field names and values

B Compilation error: missing field Year

C Runtime panic: invalid type conversion

D No error, prints {Toyota 2020}

💡 Hint

Check how struct fields are initialized with names and values.

The struct is correctly initialized with named fields. This code compiles and prints {Toyota 2020}.

❓ Predict Output

advanced

Output of nested structs

What is the output of this Go program?

Go

package main
import "fmt"
type Address struct {
  City  string
  State string
}
type User struct {
  Name    string
  Address Address
}
func main() {
  u := User{Name: "Bob", Address: Address{City: "NYC", State: "NY"}}
  fmt.Println(u.Address.City)
}

A NY

B NYC

C {City: NYC, State: NY}

D Compilation error

💡 Hint

Look at which nested field is printed.

The program prints u.Address.City which is "NYC".

🧠 Conceptual

expert

Number of fields in an anonymous struct

How many fields does this struct have?

Go

var s = struct {
  A int
  B string
  C struct {
    D float64
    E bool
  }
}{}

A 3

B 5

C 2

D 4

💡 Hint

Count only the top-level fields of the struct.

The struct has three top-level fields: A, B, and C. The nested struct inside C is one field itself.