How to parse JSON Array of JSON Hashes in GOLANG

Question

i have the following json array of json hashes :

[
  {
    "name": "XXXX",
    "address": "XXXX",
    "keepalive": {
      "thresholds": {
        "warning": 30,
        "critical": 100
      },
      "handlers": [
        "XXXXX"
      ],
      "refresh": 180
    },
    "subscriptions": [
      "XXXX",
      "XXXX",
      "XXXX"
    ],
    "version": "0.17.1",
    "timestamp": 1486413490
  },
  {...}, 
  {...},
...
]

And am parsing the array as the following :

type Client struct {
    Name string `json:"name"`
    Address string `json:"address"`
    PublicDNS string `json:"publicDNS"`
    keepalive [] string `json:"keepalive"`
    Subscriptions [] string `json:"subscriptions"`
    Version string `json:"version"`
    Timestamp int64 `json:"timestamp"`
}

type ClientResponse []Client


func getClients(body []byte) (*ClientResponse, error) {
    var s = new(ClientResponse)
    err := json.Unmarshal(body, &s)
    if(err != nil){
        fmt.Println("whoops:", err)
    }
    return s, err
}


func main() {
    res,err := http.Get("http://xxxxx:4567/clients")
    if err != nil{
        panic(err.Error())
    }

    body,err := ioutil.ReadAll(res.Body)
    if err != nil{
        panic(err.Error())
    }
    s, err := getClients([]byte(body))  
    fmt.Println(s)
}

Problem : variable s , contain all arrays . so how can i get lets say name value for all arrays ? should i do for loop and get values i need ? is this the best approach ?

Kaedys · Accepted Answer · 2017-02-06 21:44:52Z

1

You'll have to loop over them.

names := make([]string, len(*s))
for i := range *s {
    names[i] = (*s)[i].Name
}

Incidentally, your structure for unmarshalling is incorrect. keepalive isn't exported, so it won't be unmarshalled, and even if it were, it's defined as a slice of strings, while the keepalive field in the JSON is an object with thresholds, handlers, and refresh fields

edited Feb 6, 2017 at 21:44

answered Feb 6, 2017 at 21:33

Kaedys

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4 Comments

uno-2017 Over a year ago

cannot range over s (type *ClientResponse)

Kaedys Over a year ago

Ahhh, you made a named type of the slice. Should be able to range over *s, though. Incidentally, pointers to slices are almost never useful, since slices themselves are just 3-word structures, so you're only saving 2 words of data in exchange for an additional layer of indirection.

uno-2017 Over a year ago

seems ok now , thanks .. what is the best approach for such arrays ? i mean you are saying "pointers to slices are almost never useful" i did that because i was getting error : cannot unmarshal array into Go value of type main.Client

Kaedys Over a year ago

Don't unmarshal it into a Client, unmarshal it directly into a slice []Client. Example: play.golang.org/p/-e6ypRch1N

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