How do I access deeply embedded json objects from a go map object?

Question

I am new to go and I understand how to marshall json data into custom predefined Struct types but I'm currently working with a JSON set that can have dynamic keys & values with every call. I can marshall this dynamic data into a map/interface no problem but I'm a little lost with how to access the item that are deeply nested in an array.

Here is sample JSON that I'm working with from the USDOL website

    {
    "name": "osha-establishment",
    "count": 15,
    "frequency": "Manual Crawl",
    "version": 4,
    "newdata": true,
    "lastrunstatus": "success",
    "lastsuccess": "Mon Dec 08 2014 11:19:57 GMT+0000 (UTC)",
    "thisversionstatus": "success",
    "results": {
                    "est_search": [
                                    {
                                    "est_name": "Chipotle Mexican Grill",
                                    "state": "MN",
                                    "activity": {
                                        "href": "https://www.osha.gov/pls/imis/establishment.inspection_detail?id=317911832",
                                        "text": "317911832"
                                    },
                                    "opened": "11/20/2014",
                                    "rid": "0552700",
                                    "type": "Complaint",
                                    "sc": "Partial",
                                    "sic": {
                                        "href": "https://www.osha.gov/pls/imis/sic_manual.display?id=44&tab=description",
                                        "text": "5812"
                                    },
                                    "naics": "722110",
                                    "vio": ""
                                    },
                                    {
                                    "est_name": "Chipotle Mexican Grill, Inc.",
                                    "state": "AZ",
                                    "activity": {
                                        "href": "https://www.osha.gov/pls/imis/establishment.inspection_detail?id=317801066",
                                        "text": "317801066"
                                    },
                                    "opened": "07/14/2014",
                                    "rid": "0950411",
                                    "type": "Complaint",
                                    "sc": "Partial",
                                    "sic": {
                                        "href": "https://www.osha.gov/pls/imis/sic_manual.display?id=44&tab=description",
                                        "text": "5812"
                                    },
                                    "naics": "722211",
                                    "vio": "2"
                                    }
                                ]
                }
    }

I'd like to access the values of the sic keys in this JSON set.

Here is my broke go code:

package main

    import (
        "encoding/json"
        "log"
        "net/http"
    )

    func main() {
        resp, err := http.Get("https://www.kimonolabs.com/api/2oowt0xq?apikey=")

        if err != nil {
            // handle error
        }
        defer resp.Body.Close()

        var result map[string]interface{}

        dec := json.NewDecoder(resp.Body)
        if err := dec.Decode(&result); err != nil {
            // handle error
            log.Println("This is an error")
        }

        log.Println(result["results"].(map[string]interface{})["est_search"], err)

    }

Any help showing me how to access the sic values would be greatly appreciated.

Alper · Accepted Answer · 2014-12-22 03:20:16Z

To decode JSON into an interface value, Decode stores one of these in the interface value:

1. bool, for JSON booleans
2. float64, for JSON numbers
3. string, for JSON strings
4. []interface{}, for JSON arrays
5. map[string]interface{}, for JSON objects
6. nil for JSON null

According to rules above,

result["results"].(map[string]interface{})["est_search"] is []interface{} from JSON array (rule 4).
iterate over result["results"].(map[string]interface{})["est_search"].([]interface{}), each item is map[string]interface{} from JSON object (rule 5).

Here is the example code, I ran it and it seems to work with that URL;

package main

import (
    "fmt"
    "encoding/json"
    "net/http"
)

func main() {
    resp, err := http.Get("https://www.kimonolabs.com/api/2oowt0xq?apikey=DTgSLPbfOPauuLCXTws5jquLQd0V7kBB")

    if err != nil {
        // handle error
    }   
    defer resp.Body.Close()

    var result map[string]interface{}

    dec := json.NewDecoder(resp.Body)
    if err := dec.Decode(&result); err != nil {
        // handle error
        fmt.Println("This is an error")
    }   

    for _, item := range result["results"].(map[string]interface{})["est_search"].([]interface{}) {
        fmt.Println(item.(map[string]interface{})["sic"])
    }   
}

This makes sense to me now. I knew that I had to iterate but I didn't realize I had to cast the array into interface. This explanation cleared this up for me.

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