动态创建一个结构体。

huangapple go评论87阅读模式
英文:

Go creating a structure dynamically

问题

这个脚本无法正常工作。我如何通过获取传入变量的类型(例如proc.ReadStat的类型是*linux.Stat,可以通过reflect.TypeOf()显示)动态创建一个新的结构体?

package main

import (
    "fmt"
    "reflect"
    "log"
    "net/http"
    "encoding/json"
    "github.com/gorilla/mux"
    proc "github.com/c9s/goprocinfo/linux"
)

func sysinfo(w http.ResponseWriter, r *http.Request) {
    sstat, _ := proc.ReadStat("/proc/stat")
    sdiskstats, _ := proc.ReadDiskStats("/proc/diskstats")
    sloadavg, _ := proc.ReadLoadAvg("/proc/loadavg")
    smeminfo,_ := proc.ReadMemInfo("/proc/meminfo")
    smounts, _ := proc.ReadMounts("/proc/mounts")
    snetstat, _ := proc.ReadNetStat("/proc/net/netstat")
    sdevstat, _ := proc.ReadNetworkStat("/proc/net/dev")
    ssockstat, _ := proc.ReadSockStat("/proc/net/sockstat")
    svmstat, _ := proc.ReadVMStat("/proc/vmstat")

    type Info struct {
        stat       reflect.TypeOf(sstat)
        diskstats  reflect.TypeOf(sdiskstats)
        loadavg    reflect.TypeOf(sloadavg)
        meminfo    reflect.TypeOf(smeminfo)
        mounts     reflect.TypeOf(smounts)
        netstat    reflect.TypeOf(snetstat)
        devstat    reflect.TypeOf(sdevstat)
        sockstat   reflect.TypeOf(ssockstat)
        vmstat     reflect.TypeOf(svmstat)
    }

    type infos []Info

    info := infos{
        Info{
            stat:       reflect.TypeOf(sstat),
            diskstats:  reflect.TypeOf(sdiskstats),
            loadavg:    reflect.TypeOf(sloadavg),
            meminfo:    reflect.TypeOf(smeminfo),
            mounts:     reflect.TypeOf(smounts),
            netstat:    reflect.TypeOf(snetstat),
            devstat:    reflect.TypeOf(sdevstat),
            sockstat:   reflect.TypeOf(ssockstat),
            vmstat:     reflect.TypeOf(svmstat),
        },
    }

    json.NewEncoder(w).Encode(info)
}

func main() {
    router := mux.NewRouter().StrictSlash(true)
    router.HandleFunc("/", sysinfo)
    log.Fatal(http.ListenAndServe(":8080", router))
}

以上是翻译好的代码部分。

英文:

This script does not work. How may I create a new struc dynamically by getting the types of incoming variables like proc.ReadStat ? (type of proc.ReadStat is *linux.Stat as shown by reflect.TypeOf() )

package main
import (
"fmt"
"reflect"
//"html"
"log"
"net/http"
//"time"
"encoding/json"
"github.com/gorilla/mux"
proc "github.com/c9s/goprocinfo/linux"
)
func sysinfo(w http.ResponseWriter, r *http.Request) {
sstat, _ := proc.ReadStat("/proc/stat")
sdiskstats, _ := proc.ReadDiskStats("/proc/diskstats")
sloadavg, _ := proc.ReadLoadAvg("/proc/loadavg")
smeminfo,_ := proc.ReadMemInfo("/proc/meminfo")
smounts, _ := proc.ReadMounts("/proc/mounts")
snetstat, _ := proc.ReadNetStat("/proc/net/netstat")
sdevstat, _ := proc.ReadNetworkStat("/proc/net/dev")
ssockstat, _ := proc.ReadSockStat("/proc/net/sockstat")
svmstat, _ := proc.ReadVMStat("/proc/vmstat")
t   /* type Info interface {
stat      *linux.Stat
diskstats []linux.DiskStat
loadavg   *linux.LoadAvg
meminfo   *linux.MemInfo
mounts    *linux.Mounts
netstat   *linux.NetStat
devstat   []linux.NetworkStat
sockstat  *linux.SockStat 
vmstat    *linux.VMStat
}*/
type Info struct {
stat       reflect.TypeOf(sstat)
diskstats  reflect.TypeOf(sdiskstats)
loadavg    reflect.TypeOf(sloadavg)
meminfo    reflect.TypeOf(smeminfo)
mounts     reflect.TypeOf(smounts)
netstat    reflect.TypeOf(snetstat)
devstat    reflect.TypeOf(sdevstat)
sockstat   reflect.TypeOf(ssockstat)
vmstat     reflect.TypeOf(svmstat)
}
type infos []Info
infos := info{
stat : sstat,
diskstats : sdiskstats,
loadavg : sloadavg,
meminfo : smeminfo,
mounts : smounts,
netstat : snetstat,
devstat : sdevstat,
sockstat : ssockstat,
vmstat : svmstat,
}
json.NewEncoder(w).Encode(infos)
}
func main() {
router := mux.NewRouter().StrictSlash(true)
router.HandleFunc("/", sysinfo)
log.Fatal(http.ListenAndServe(":8080", router))
}

答案1

得分: 1

在静态类型语言中(Go 是其中之一),类型信息(变量、字段等的类型信息)必须在编译时存在,所以你不能像这样做:

type Info struct {
    stat       reflect.TypeOf(sstat)
}

因为 reflect.TypeOf() 是一个在运行时执行的函数。如果你不知道某个东西的类型,可以使用 interface{},但是编译器将无法进行编译时类型检查。

由于你只想要编组结果,你可以将字段的类型设置为 interface{}。还要注意,字段名必须是公开的(必须以大写字母开头),才能包含在 JSON 输出中。

所以尝试以下代码:

type Info struct {
    Stat       interface{}
    Diskstats  interface{}
    Loadavg    interface{}
    Meminfo    interface{}
    Mounts     interface{}
    Netstat    interface{}
    Devstat    interface{}
    Sockstat   interface{}
    Vmstat     interface{}
}

type infos []Info

infos := info{
    Stat : sstat,
    Diskstats : sdiskstats,
    Loadavg : sloadavg,
    Meminfo : smeminfo,
    Mounts : smounts,
    Netstat : snetstat,
    Devstat : sdevstat,
    Sockstat : ssockstat,
    Vmstat : svmstat,
}

json.NewEncoder(w).Encode(infos)

注意,你也可以使用简单的 map[string]interface{}

infos := map[string]interface{}{
    "stat" : sstat,
    "diskstats" : sdiskstats,
    "loadavg" : sloadavg,
    "meminfo" : smeminfo,
    "mounts" : smounts,
    "netstat" : snetstat,
    "devstat" : sdevstat,
    "sockstat" : ssockstat,
    "vmstat" : svmstat,
}
json.NewEncoder(w).Encode(infos)

另外,请不要忘记处理错误:存储返回的错误并检查它们是否为 nil

英文:

In statically typed languages (Go is one of them) type info (of variables, fields etc.) have to be present and compile-time, so you can't do something like:

type Info struct {
stat       reflect.TypeOf(sstat)
}

Because reflect.TypeOf() is a function which will run at run-time. If you don't know the type of something, you may use interface{}, but then you won't get any compile-time type checking from the compiler.

Since you just want to marshal the results, you can use interface{} as the type of the fields. Also note that field names must be exported (must start with a capital letter) in order to be included in JSON output.

So try the following:

type Info struct {
Stat       interface{}
Diskstats  interface{}
Loadavg    interface{}
Meminfo    interface{}
Mounts     interface{}
Netstat    interface{}
Devstat    interface{}
Sockstat   interface{}
Vmstat     interface{}
}
type infos []Info
infos := info{
Stat : sstat,
Diskstats : sdiskstats,
Loadavg : sloadavg,
Meminfo : smeminfo,
Mounts : smounts,
Netstat : snetstat,
Devstat : sdevstat,
Sockstat : ssockstat,
Vmstat : svmstat,
}
json.NewEncoder(w).Encode(infos)

Note that you could also just use a simple map[string]interface{}:

infos := map[string]interface{}{
"stat" : sstat,
"diskstats" : sdiskstats,
"loadavg" : sloadavg,
"meminfo" : smeminfo,
"mounts" : smounts,
"netstat" : snetstat,
"devstat" : sdevstat,
"sockstat" : ssockstat,
"vmstat" : svmstat,
}
json.NewEncoder(w).Encode(infos)

Also please do not forget about and do not omit error handling: store returned errors and check whether they are nil!

huangapple
  • 本文由 发表于 2015年11月20日 18:32:34
  • 转载请务必保留本文链接:https://go.coder-hub.com/33824410.html
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