策略模式：使用共享数据结构传递参数

package main

import "fmt"

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


// Concrete Strategy
type PayPalStrategy struct{}


func (p *PayPalStrategy) Pay(data *PaymentData) string {
  return fmt.Sprintf("Paid %d using PayPal. PayPal user: %s", data.Amount, data.PayPalData.User)
}


// Concrete Strategy
type CreditCardStrategy struct{}


func (c *CreditCardStrategy) Pay(data *PaymentData) string {
  return fmt.Sprintf("Paid %d using Credit Card. Card Number: %s", data.Amount, data.CreditCardData.CardNumber)
}


// Context
type ShoppingCart struct {
  data *PaymentData
}


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


// PaymentData serves as the shared data structure for payment strategies
type PaymentData struct {
  Strategy         PaymentStrategy
  Amount           int
  PayPalData       *PayPalData
  CreditCardData   *CreditCardData
}


type PayPalData struct {
  User string
}


type CreditCardData struct {
  CardNumber string
}


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


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