Golang装饰器模式实现功能动态增强

type Logger interface {
    Log(msg string)
}

type ConsoleLogger struct{}

func (c ConsoleLogger) Log(msg string) {
    fmt.Println("[CONSOLE]", msg)
}

type TimestampLogger struct {
    logger Logger // 持有被装饰对象
}

func (t TimestampLogger) Log(msg string) {
    now := time.Now().Format("2006-01-02 15:04:05")
    t.logger.Log(fmt.Sprintf("[%s] %s", now, msg)) // 前置增强
}

type CountingLogger struct {
    logger Logger
    count  int
}

func (c *CountingLogger) Log(msg string) {
    c.count++
    fmt.Printf("[COUNT:%d] ", c.count)
    c.logger.Log(msg)
}

func WithTimestamp(logger Logger) Logger {
    return TimestampLogger{logger: logger}
}

func WithCounting(logger Logger) Logger {
    return &CountingLogger{logger: logger}
}

base := ConsoleLogger{}
logger := WithTimestamp(WithCounting(base))

logger.Log("user logged in") 
// 输出：[COUNT:1] [2024-06-10 14:22:33] user logged in

func WithTiming[T any](f func(T) T) func(T) T {
    return func(t T) T {
        start := time.Now()
        result := f(t)
        fmt.Printf("took %v\n", time.Since(start))
        return result
    }
}