Metodlar

Metod — bu ma’lum bir turga (type) biriktirilgan funksiya. Oddiy funksiyadan farqi shundaki, nomidan oldin receiver turadi — metod qaysi turga tegishli ekanini ko’rsatadigan qism. Receiver ikki xil bo’ladi: value (r Counter) nusxa ustida ishlaydi, pointer (r *Counter) esa asl qiymatni o’zgartiradi.

package main
 
import "fmt"
 
type Counter struct {
    Count int
}
 
func (c Counter) IncByValue()    { c.Count++ } // nusxa - asl qiymat o'zgarmaydi
func (c *Counter) IncByPointer() { c.Count++ } // pointer - asl qiymat o'zgaradi
 
func main() {
    c := Counter{}
 
    c.IncByValue()
    fmt.Println("value receiverdan keyin:", c.Count)
 
    c.IncByPointer() // Go o'zi (&c) ni oladi
    fmt.Println("pointer receiverdan keyin:", c.Count)
}

$ go run receivers.go
value receiverdan keyin: 0
pointer receiverdan keyin: 1

Xulosa: agar metod structni o’zgartirsa yoki struct katta bo’lsa — pointer receiver ishlating; kichik, o’zgarmaydigan turlar uchun value receiver ham yetadi. Chalkashmaslik uchun bitta turning hamma metodini bir xil receiver bilan yozing.

Metodni faqat structga emas, o’z paketingizda e’lon qilgan istalgan turga biriktirish mumkin — masalan float64 ustiga qurilgan turga:

package main
 
import "fmt"
 
type Celsius float64
 
func (c Celsius) ToFahrenheit() float64 {
    return float64(c)*9/5 + 32
}
 
func main() {
    var t Celsius = 25
    fmt.Printf("%.1f°C = %.1f°F\n", float64(t), t.ToFahrenheit())
}

$ go run named-type.go
25.0°C = 77.0°F

Xulosa: int yoki string kabi tayyor turlarga to’g’ridan-to’g’ri metod qo’sha olmaysiz — avval ular ustiga o’zingizning typeingizni yaratib olishingiz kerak.

Manba / batafsil: Go spec — Method declarations