Embedding

Go’da meros (inheritance) yo’q — uning o’rniga kompozitsiya ishlatiladi. Embedding shunaqa ishlaydi: bitta structni ikkinchisining ichiga nom bermay joylashtirasiz, shunda uning maydonlari (field) va metodlari xuddi tashqi structniki bo’lib qoladi. Buni “method promotion” deb atashadi.

embed.go


package main
 
import "fmt"
 
type Engine struct {
    Power int
}
 
func (e Engine) Start() {
    fmt.Printf("Dvigatel ishga tushdi (%d ot kuchi)\n", e.Power)
}
 
type Car struct {
    Engine // embedded - maydon nomi yo'q
    Brand  string
}
 
func main() {
    c := Car{Engine: Engine{Power: 150}, Brand: "Chevrolet"}
 
    c.Start()             // metod Engine dan ko'tarildi
    fmt.Println(c.Power)  // maydon ham ko'tarildi
    fmt.Println(c.Brand)
}


$ go run embed.go
Dvigatel ishga tushdi (150 ot kuchi)
150
Chevrolet

Xulosa: Car Engineni meros qilib olgani yo’q — uni o’z ichiga oldi, xolos. Uning maydon va metodlari esa c.Power, c.Start() bo’lib yuqoriga “ko’tarildi”. Agar tashqi structda xuddi shu nomli metod bo’lsa, o’sha ustun turadi.

Interfeyslarni (interface) ham bir-birining ichiga joylashtirish mumkin — kichiklaridan kattaroq interfeys yig’iladi (standart kutubxonadagi io.ReadWriter aynan shunday tuzilgan):

iface-embed.go


package main
 
import "fmt"
 
type Reader interface{ Read() string }
type Writer interface{ Write(s string) }
 
type ReadWriter interface { // ikkalasini birlashtiradi
    Reader
    Writer
}
 
type Buffer struct{ data string }
 
func (b *Buffer) Read() string  { return b.data }
func (b *Buffer) Write(s string) { b.data = s }
 
func main() {
    var rw ReadWriter = &Buffer{}
    rw.Write("embedding kuchli")
    fmt.Println(rw.Read())
}


$ go run iface-embed.go
embedding kuchli

Xulosa: *Buffer ikkala interfeysning metodlarini ham yozgan, shu bois birlashgan ReadWriterni to’liq qondiradi.

Manba / batafsil: Effective Go — Embedding