[Go] golang x.(type) 用法

func MyPrintf(args ...interface{}) {  
    for _, arg := range args {  
        switch arg.(type) {  
            case int:  
                fmt.Println(arg, "is an int value.")  
            case string:  
                fmt.Println(arg, "is a string value.")  
            case int64:  
                fmt.Println(arg, "is an int64 value.")  
            default:  
                fmt.Println(arg, "is an unknown type.")  
        }  
    }  
}

        switch h := p.Header.(type) {
        case *mail.InlineHeader:
            // This is the message's text (can be plain-text or HTML)
            b, _ := ioutil.ReadAll(p.Body)
            log.Println("Got text: ", string(b))
        case *mail.AttachmentHeader:
            // This is an attachment
            filename, _ := h.Filename()
            log.Println("Got attachment: ", filename)
        }