策略模式：使用参数对象传递参数

package main


import "fmt"


// Strategy Interface
type PaymentStrategy interface {
  Pay(data interface{}) string
}


// Concrete Strategy
type PayPalStrategy struct{}


func (p *PayPalStrategy) Pay(data interface{}) string {
  payPalData, ok := data.(*PayPalData)
  if !ok {
    return "Invalid data for PayPalStrategy"
  }
  return fmt.Sprintf("Paid %d using PayPal. PayPal user: %s", payPalData.Amount, payPalData.User)
}


// Concrete Strategy
type CreditCardStrategy struct{}


func (c *CreditCardStrategy) Pay(data interface{}) string {
  creditCardData, ok := data.(*CreditCardData)
  if !ok {
    return "Invalid data for CreditCardStrategy"
  }
  return fmt.Sprintf("Paid %d using Credit Card. Card Number: %s", creditCardData.Amount, creditCardData.CardNumber)
}


// Context
type ShoppingCart struct {
  strategy PaymentStrategy
  data     interface{}
}


func (s *ShoppingCart) checkout() string {
  return s.strategy.Pay(s.data)
}


// Parameter objects for different strategies
type PayPalData struct {
  Amount int
  User   string
}


type CreditCardData struct {
  Amount     int
  CardNumber string
}


func main() {
  data := &PayPalData{Amount: 200, User: "user@example.com"}
  cart := &ShoppingCart{strategy: &PayPalStrategy{}, data: data}
  fmt.Println(cart.checkout()) // Paid 200 using PayPal. PayPal user: user@example.com


  data = &CreditCardData{Amount: 300, CardNumber: "1234-5678-9012-3456"}
  cart = &ShoppingCart{strategy: &CreditCardStrategy{}, data: data}
  fmt.Println(cart.checkout()) // Paid 300 using Credit Card. Card Number: 1234-5678-9012-3456
}