Golang error: interface conversion: interface {} is bool/float..., not string - json

Question

I am trying to decode an arbitrary JSON using Golang, so I unmarshal the incoming JSON in a map[string]interface{} as shown in the code below:
func JsonHandler(jsonRequest []byte) {
// Creating the maps for JSON
var m interface{}
// Parsing/Unmarshalling JSON encoding/json
if err := json.Unmarshal([]byte(jsonRequest), &m); err != nil {
panic(err)
}
//Creating an output file for writing
f, err := os.OpenFile("/home/dorrahadrich/Desktop/output.txt", os.O_APPEND|os.O_WRONLY|os.O_CREATE, 0600)
if err != nil {
panic(err)
}
defer f.Close()
ParseJson(m, f, err)
}
func ParseJson(m interface{}, f *os.File, err error) {
switch v := m.(interface{}).(type){
case map[string]interface{}:
ParseMap (m.(map[string]interface{}),f,err)
fmt.Println(v)
case []interface{}:
ParseArray (m.([]interface{}),f,err)
fmt.Println(v)
default:
}
}
func ParseMap(aMap map[string]interface{}, f *os.File, err error) {
for key, val := range aMap {
switch val.(type) {
case map[string]interface{}:
if _, err = f.WriteString(key + "={\n"); err != nil {
panic(err)
}
ParseMap(val.(map[string]interface{}), f, err)
//Close brackets
if _, err = f.WriteString("};\n"); err != nil {
panic(err)
}
case []interface{}:
//Write to file
if _, err = f.WriteString(key + "={\n"); err != nil {
panic(err)
}
ParseArray(val.([]interface{}), f, err)
//Close brackets
if _, err = f.WriteString("};\n"); err != nil {
panic(err)
}
default:
otherValues(key, val.(interface{}), f , err)
}
}
}
func ParseArray(anArray []interface{}, f *os.File, err error) {
for _, val := range anArray {
switch val.(type) {
case map[string]interface{}:
ParseMap(val.(map[string]interface{}), f, err)
case []interface{}:
ParseArray(val.([]interface{}), f, err)
default:
}
}
}
func otherValues(key string, other interface{}, f *os.File, err error) {
if _, err = f.WriteString(key); err != nil {
panic(err)
}
if _, err = f.WriteString("="); err != nil {
panic(err)
}
switch other.(interface{}).(type) {
case string:
if _, err = f.WriteString(other.(string)); err != nil {
panic(err)
}
case float64:
if _, err = f.WriteString(strconv.FormatFloat(other.(float64), 'f', -1, 64)); err != nil {
panic(err)
}
case bool:
if _, err = f.WriteString(strconv.FormatBool(other.(bool))); err != nil {
panic(err)
}
default:
}
}
The problem is that whenever a JSON contains a bool/int/float or any not string value the program panics saying that it fails converting an interface to the given type! Please note that the JSON is arbitrary so I don't have any idea about the keys nor the values, I can't unmrashal into an interface nor access the values giving a path.

Answer 1

The error says it all:
interface conversion: interface{} is bool/float64
when you are unmarshalling json the values for int and bool which are not of interface type. In your switch add case for bool/float64/string too. Since json is arbitrary unmarshal them using interface{}.
func otherValues(other interface{}, f *os.File, err error) {
switch bb := other.(interface{}).(type) {
case string:
fmt.Println("This is a string")
case float64:
fmt.Println("this is a float")
case bool:
fmt.Println("this is a boolean")
default:
fmt.Printf("Default value is of type %v", bb)
}
}
Use file.Write in place of file.WriteString
func (f *File) Write(b []byte) (n int, err error)
Write writes len(b) bytes to the File. It returns the number of bytes
written and an error, if any. Write returns a non-nil error when n !=
len(b).