如何在Golang中实现策略模式动态切换算法

type PaymentStrategy interface {
    Pay(amount float64) string
}

type CreditCardStrategy struct {
    Name string
}

func (c *CreditCardStrategy) Pay(amount float64) string {
    return fmt.Sprintf("Paid %.2f using Credit Card by %s", amount, c.Name)
}

type PayPalStrategy struct {
    Email string
}

func (p *PayPalStrategy) Pay(amount float64) string {
    return fmt.Sprintf("Paid %.2f using PayPal account %s", amount, p.Email)
}
</font>

<H3>上下文管理策略切换</H3>
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<font face="Courier New">
<pre class="brush:php;toolbar:false;">
type PaymentContext struct {
    strategy PaymentStrategy
}

func (p *PaymentContext) SetStrategy(s PaymentStrategy) {
    p.strategy = s
}

func (p *PaymentContext) ExecutePayment(amount float64) string {
    if p.strategy == nil {
        return "No strategy set"
    }
    return p.strategy.Pay(amount)
}
</font>

<p>这样可以在程序运行中随时更换算法：</p>
<font face="Courier New">
<pre class="brush:php;toolbar:false;">
context := &PaymentContext{}

// 使用信用卡支付
context.SetStrategy(&CreditCardStrategy{Name: "Alice"})
fmt.Println(context.ExecutePayment(100.0))

// 切换为PayPal支付
context.SetStrategy(&PayPalStrategy{Email: "alice@example.com"})
fmt.Println(context.ExecutePayment(80.0))

func GetStrategyByUserType(userType string) PaymentStrategy {
    switch userType {
    case "premium":
        return &CreditCardStrategy{Name: "VIP User"}
    case "basic":
        return &PayPalStrategy{Email: "user@example.com"}
    default:
        return &CreditCardStrategy{Name: "Guest"}
    }
}

strategy := GetStrategyByUserType("basic")
context.SetStrategy(strategy)