Type Assertion

Interfeys ichida haqiqiy qiymat ham, uning turi (type) ham yashiringan bo’ladi — masalan any ichida int bormi yoki stringmi, bilmaymiz. Type assertion — ya’ni qiymat.(Tur) shakli — asl qiymatni kerakli turga chiqarib beradi. Oddiy shakli, agar tur mos kelmasa, panic beradi, shuning uchun xavfsiz comma-ok shaklini ishlatamiz: ikkinchi qiymat (ok) tur mos kelgan-kelmaganini bildiradi.

comma-ok.go


package main
 
import "fmt"
 
func main() {
    var i any = "gopher"
 
    if s, ok := i.(string); ok {
        fmt.Println("string:", s)
    }
 
    if n, ok := i.(int); ok { // noto'g'ri tur - panic emas, ok=false
        fmt.Println("int:", n)
    } else {
        fmt.Println("bu int emas")
    }
}


$ go run comma-ok.go
string: gopher
bu int emas

Xulosa: comma-ok’da tur mos kelmasa dastur qulab tushmaydi — shunchaki ok false bo’ladi, xolos.

Bir nechta turni tekshirish kerak bo’lsa, switchning maxsus shakli — type switch (qiymat.(type)) ancha toza yechim beradi. Har bir case ichida o’zgaruvchi avtomatik o’sha turda bo’ladi:

type-switch.go


package main
 
import "fmt"
 
func describe(v any) {
    switch x := v.(type) {
    case int:
        fmt.Printf("butun son: %d\n", x*2)
    case string:
        fmt.Printf("matn, uzunligi %d\n", len(x))
    case nil:
        fmt.Println("qiymat yo'q (nil)")
    default:
        fmt.Printf("noma'lum tur: %T\n", x)
    }
}
 
func main() {
    describe(42)
    describe("salom")
    describe(3.14)
    describe(nil)
}


$ go run type-switch.go
butun son: 84
matn, uzunligi 5
noma'lum tur: float64
qiymat yo'q (nil)

Xulosa: type switch — any yoki umumiy interfeys orqali kelgan qiymatni turiga qarab ishlashning eng toza usuli.

Manba / batafsil: Go spec — Type assertions , Type switches