Parsing a JSON file in Go

Question

I am having trouble parsing a JSON file in Go.

I am not getting any errors, but I am not getting an output.

I have tried a few different methods, but I can't seem to get any to work. Any help would be greatly appreciated. Thanks in advance.

package simplefiles

import (
    "encoding/json"
    "fmt"
    "os"
)

//PluginInfo - struct for plugins.json
var PluginInfo struct {
    LatestVersion   string   `json:"latest_version"`
    LastUpdated     string   `json:"last_updated"`
    Popular         bool     `json:"popular"`
    Info            []string `json:"Info"`
}

//ParsePlugins - parses plugins.json
func ParsePlugins() {
    pluginsFile, err := os.Open("test.json")
    if err != nil {
        fmt.Println("opening config file", err.Error())
    }
    jsonParser := json.NewDecoder(pluginsFile)
    if err = jsonParser.Decode(&PluginInfo); err != nil {
        fmt.Println("parsing config file", err.Error())
    } else {
        fmt.Printf(PluginInfo.LastUpdated)
    }
    return
}

JSON Sample:

{  
   "my-test-site":{  
      "latest_version":"6.4.5",
      "last_updated":"2016-05-22T00:23:00.000Z",
      "popular":true,
      "infomation":[  
         {  
            "id":6043,
            "title":"Test info 1",
            "created_at":"2014-08-01T10:58:35.000Z",
            "updated_at":"2015-05-15T13:47:24.000Z",
            "published_date":null,
            "references":{  
               "url":[  
                  "http://samplesite1.com",
                  "http://samplesite2.com"
               ]
            },
            "site_type":"info",
            "fixed_v":"1.10"
         }
      ]
   },
   "another-test-site":{  
      "latest_version":"2.1.0",
      "last_updated":"2016-06-12T08:36:00.000Z",
      "popular":false,
      "infomation":[  
         {  
            "id":6044,
            "title":"Test site 2 info",
            "created_at":"2014-08-01T10:58:35.000Z",
            "updated_at":"2015-05-15T13:47:24.000Z",
            "published_date":null,
            "references":{  
               "otherinfo":[  
                  "blah blah blah"
               ]
            },
            "site_type":"search",
            "fixed_v":"1.2.0"
         }
      ]
   }
}

Answer 1

Your problem is that your JSON data is a map of string to the struct type you defined, not the struct type directly. If you modify your code slightly as below it works, but you need to index into the map to get each struct value:

package main

import (
        "encoding/json"
        "fmt"
        "os"
)

//PluginInfo - struct for plugins.json
var PluginInfo map[string]struct { // NOTICE map of string to struct
        LatestVersion string   `json:"latest_version"`
        LastUpdated   string   `json:"last_updated"`
        Popular       bool     `json:"popular"`
        Info          []string `json:"Info"`
}

//ParsePlugins - parses plugins.json
func ParsePlugins() {
        pluginsFile, err := os.Open("test.json")
        if err != nil {
                fmt.Println("opening config file", err.Error())
        }
        jsonParser := json.NewDecoder(pluginsFile)
        if err = jsonParser.Decode(&PluginInfo); err != nil {
                fmt.Println("parsing config file", err.Error())
        } else {
                for key, val := range PluginInfo {
                        fmt.Printf("Key %q, last updated %s\n", key, val.LastUpdated)
                }
        }
        return
}

func main() {
        ParsePlugins()
}