Strategy

Muammo: bitta vazifani bajarishning bir necha usuli bor (turlicha saralash, turlicha to’lov, turlicha siqish) va ularni ish vaqtida almashtira olish kerak. Kodni if/else shoxlari bilan to’ldirmaslik lozim.

G’oya: har bir usulni alohida “strategiya” qilib ajratasiz va kerakligini uzatasiz. Go da strategiya ko’pincha shunchaki funksiya qiymati - alohida interfeys yoki class shart emas.

strategy.go


package main
 
import (
	"fmt"
	"sort"
)
 
type Product struct {
	Name  string
	Price int
}
 
// Strategy - shunchaki funksiya turi.
type SortStrategy func(a, b Product) bool
 
func ByPrice(a, b Product) bool { return a.Price < b.Price }
func ByName(a, b Product) bool  { return a.Name < b.Name }
 
type Catalog struct {
	products []Product
	sortBy   SortStrategy
}
 
func (c *Catalog) SetStrategy(s SortStrategy) { c.sortBy = s }
 
func (c *Catalog) Sorted() []Product {
	out := make([]Product, len(c.products))
	copy(out, c.products)
	sort.Slice(out, func(i, j int) bool { return c.sortBy(out[i], out[j]) })
	return out
}
 
func main() {
	c := &Catalog{products: []Product{
		{"Klaviatura", 350000},
		{"Sichqoncha", 120000},
		{"Monitor", 1500000},
	}}
 
	c.SetStrategy(ByPrice)
	fmt.Println("Narx bo'yicha:", names(c.Sorted()))
 
	c.SetStrategy(ByName)
	fmt.Println("Nom bo'yicha: ", names(c.Sorted()))
}
 
func names(ps []Product) []string {
	out := make([]string, len(ps))
	for i, p := range ps {
		out[i] = p.Name
	}
	return out
}


$ go run strategy.go
Narx bo'yicha: [Sichqoncha Klaviatura Monitor]
Nom bo'yicha:  [Klaviatura Monitor Sichqoncha]

Xatti-harakatni SetStrategy bilan ish vaqtida almashtirdik, Sortedni umuman o’zgartirmadik.

Qachon: o’zaro almashinadigan algoritmlar kerak bo’lganda. Go note: funksiya - birinchi darajali qiymat bo’lgani uchun Strategy ko’pincha bitta func ga qisqaradi (sort.Slice, http.HandlerFunc shu g’oyada).

Manba / batafsil: refactoring.guru/design-patterns/strategy