使用指针作为函数的参数

Question

How can I use methods of function arguments?

func writeToInflux(c interface{}, host string, service string, state string) bool {
    fmt.Println(reflect.TypeOf(c), host, service)

    bp, e := client.NewBatchPoints(client.BatchPointsConfig{
        Database:  database,
        Precision: "us",
    })

    if e != nil {
        log.Print(e)
    }

    tags := map[string]string{
        "host":    host,
        "service": service,
    }

    fields := map[string]interface{}{
        "state": state,
    }

    pt, err := client.NewPoint("mon", tags, fields, time.Now())

    if err != nil {
        log.Print(err)
    }

    bp.AddPoint(pt)

    if err := c.Write(bp); err != nil {
        log.Print("write failed " + err)
    }

    return true
}

func handler(w http.ResponseWriter, r *http.Request) {
    c, err := client.NewHTTPClient(client.HTTPConfig{
        Addr:     "http://10.x.x.x:8086",
        Username: username,
        Password: password,
    })
    if err != nil {
        log.Print(err)
    }
    a := strings.Split(r.URL.Path, "/")
    writeToInflux(c, a[3], a[4], a[5])
}

In this example i can't use parameters of c variable, or maybe there is another options to use c as parameter to function?

Answer 1

"c" is an interface{} type, Having an interface in function parameter, you can able to pass any struct or any data types into it.

In your case you want c to use the function write
if err := c.Write(bp); err != nil {
        log.Print("write failed " + err)
    }

The compiler doesn't know the type of c, so you need to type assert it.

Try this, It will work

newC,ok:=  c.(type of c)    type of C -> a struct or any type which has a method write

if ok {
    if err := newC.Write(bp); err != nil {
            log.Print("write failed " + err)
        }

}     

Or Change your function like this

func writeToInflux(c client.Client, host string, service string, state string) bool