Struct usage patterns in Go - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of embedded struct field access

What is the output of this Go program?

Go

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

A Paris

B Compilation error: ambiguous selector

C Runtime panic

D Empty string

💡 Hint

Embedded structs allow direct access to their fields.

In Go, embedding a struct allows you to access its fields directly from the outer struct. Here, p.City accesses Address.City.

❓ Predict Output

intermediate

Output of struct pointer modification

What will be printed by this Go program?

Go

package main
import "fmt"
type Counter struct {
    Count int
}
func (c *Counter) Increment() {
    c.Count++
}
func main() {
    c := Counter{Count: 5}
    c.Increment()
    fmt.Println(c.Count)
}

A Compilation error: cannot call pointer method on value

B 5

C 6

D Runtime panic

💡 Hint

Pointer receiver methods can be called on values; Go handles the address automatically.

Go automatically takes the address of c to call the pointer receiver method Increment, which increments Count from 5 to 6.

🔧 Debug

advanced

Identify the cause of compilation error

This Go code fails to compile. What is the cause?

Go

package main
import "fmt"
type Data struct {
    value int
}
func main() {
    d := Data{value: 10}
    fmt.Println(d.Value)
}

A Missing import for fmt package

B Variable d is not initialized

C Cannot print struct field directly

D Field 'Value' does not exist; Go is case-sensitive

💡 Hint

Check the exact spelling and capitalization of struct fields.

Go is case-sensitive. The struct field is named 'value' (lowercase), but the code tries to access 'Value' (uppercase), causing a compilation error.

🧠 Conceptual

advanced

Effect of struct value vs pointer receiver on method behavior

Consider a struct with two methods: one with a value receiver and one with a pointer receiver. Which statement is true about their behavior when called on a struct value?

A Both methods modify the original struct

B The pointer receiver method can modify the original struct; the value receiver method works on a copy

C Neither method can modify the original struct

D Value receiver methods require explicit pointer conversion to be called

💡 Hint

Think about how Go passes the struct to each method type.

Value receiver methods get a copy of the struct, so changes do not affect the original. Pointer receiver methods get the address and can modify the original struct.

❓ Predict Output

expert

Output of struct embedding with method overriding

What is the output of this Go program?

Go

package main
import "fmt"
type Animal struct {}
func (a Animal) Speak() string {
    return "..."
}
type Dog struct {
    Animal
}
func (d Dog) Speak() string {
    return "Woof!"
}
func main() {
    var a Animal = Dog{}
    fmt.Println(a.Speak())
}

A ...

B Woof!

C Compilation error: cannot assign Dog to Animal

D Runtime panic

💡 Hint

Consider how method sets and interface assignments work in Go.

The variable 'a' is of type Animal, not an interface. Assigning Dog{} to Animal slices off the Dog part, so calling Speak calls Animal's method, printing "...".