How to convert a map[string]interface{} to string

Question

I'm trying to get the path to value from a json file:

for example :

x: 4
z:
  y: 6
  t: 8
a:
  b:
    p: 0
m:
  c : 4 

the output that i want is :

x=4, z.y=6, z.t=8, a.b.p=0, m.c=4

i wrote a functions below :

func parsecustom(aMap map[string]interface{}) (string, string) {

    var sol string
    var k string
    for key, val := range aMap {
        switch concreteVal := val.(type) {
        case map[string]interface{}:
            x, _ := parseMap(val.(map[string]interface{}))
            sol = key + "." + x
            k += sol + ","
        case string:
            sol = key + "=" + concreteVal + " "
            k += sol + ","
        case float64:
            sol = key + "=" + strconv.FormatFloat(concreteVal, 'f', -1, 64) + " "
            k+= sol + ","
        default:
            k = " "

        }
    }

return sol, TrimSuffix(k, ",")
}

but it didn't take into account this case :

z:
  y: 6
  t: 8

it override, it print only z.t=8 and ignore z.y=6

Any hints please how to solve this problem

Answer 1

To address the problem that child values should bearing parents' name, I think when recursing, there needs to be a prefix parameter. And instead of asking the parents to insert those prefix into the string, it would feel more normal to let the children write the prefix just as they are going to write their own parsed results. So I changed your code:

func parseMap(aMap map[string]interface{}, prefix string, b *strings.Builder) {
    var sol string
    for key, val := range aMap {
        switch concreteVal := val.(type) {
        case map[string]interface{}:
            parseMap(concreteVal,prefix+key+".",b)
        case string:
            sol = key + "=" + concreteVal + " "
            b.WriteString(prefix)
            b.WriteString(sol)
            b.WriteRune(',')
        case float64:
            sol = key + "=" + strconv.FormatFloat(concreteVal, 'f', -1, 64) + " "
            b.WriteString(prefix)
            b.WriteString(sol)
            b.WriteRune(',')
        default:
            //What?
            panic("Unsupported")
        }
    }
}

Since we are concating a lot of strings here, I used the strings.Builder for string building. b.WriteString(x) is just appeding x to the tail of the string b holds.

And because we now use a strings.builder and a prefix, so I write a function to wrap it:

func parsecustom(aMap map[string]interface{}) string {
    b:=&strings.Builder{}
    parseMap(aMap,"",b)

    return strings.TrimSuffix(b.String(),",")
}

Now if you run fmt.Println(parsecustom(data)), you can get output: x=4 ,z.t=8 ,z.y=6 ,a.b.p=0 ,m.c=4 as desired.

Full example: https://play.golang.org/p/_QIp2LRYjm7