Struct and pointer
- Go course
- Beginner
- Lesson 73/90
- 4 min
Learn struct pointers and dot access.
Structs and pointers
When accessing fields through a struct pointer you don't need to write (*p).Ad; Go does it automatically: p.Ad.
k := &Kitap{Title: "Dune", Sayfa: 412}
k.Sayfa = 500 // same as (*k).Sayfa = 500
fmt.Println(k.Sayfa) // 500Pointers are used to change a struct in a function or to pass a large struct without copying it.
Changing it in a function
If a struct is passed by value the function works on a copy; to keep the change, pass a pointer:
func zamYap(c *Calisan, oran float64) {
c.Maas *= 1 + oran
}
c := Calisan{Ad: "Ada", Maas: 1000}
zamYap(&c, 0.1)
fmt.Println(c.Maas) // 1100Practice Give a raise
Write the Calisan struct (Ad string, Maas float64) and the zamYap(c *Calisan, oran float64) function. Give a 0.1 raise to an employee with Maas: 1000 and print the salary.
Starter code
package main
import "fmt"
func main() {
// buraya yaz
}Sample solution
package main
import "fmt"
type Calisan struct {
Ad string
Maas float64
}
func zamYap(c *Calisan, oran float64) {
c.Maas *= 1 + oran
}
func main() {
c := Calisan{Ad: "Ada", Maas: 1000}
zamYap(&c, 0.1)
fmt.Println(c.Maas)
}Expected output
1100
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 What is the correct way to access a field through a struct pointer?
- p.Ad Correct answer
- p->Ad
- *p.Ad
- p::Ad
Explanation: Go dereferences the pointer automatically with the dot operator; -> and :: don't exist in Go, and *p.Ad is read as *(p.Ad).
2 Struct pointer
func zamYap(c ____Calisan, oran float64) {
c.Maas *= 1 + oran
}func zamYap(c *Calisan, oran float64) {
c.Maas *= 1 + oran
}Explanation: Making the parameter *Calisan lets the function change the real struct.
3 Code and effect
| Term | Meaning |
|---|---|
p.Ad (p *Kitap) |
Automatic dereference |
f(k) (value) |
The copy changes |
f(&k) (pointer) |
The original changes |
&Kitap{...} |
Creates a pointer |