Type switch to []map[string]interface{} on the value of map[string]interface{}

Question

Problem

I'm facing the issue to remove not required arrays from an json object eg. arrays with only one element which is not an object or array. (No arrays as root of the input)

Example

In:

{"name": [{ "inner": ["test"] }]}

Wanted Out:

{"name": [{ "inner": "test" }]}

Approach

I started with a simple type switch on the values of a parsed map[string]interface{} and recognized that it wont switch to the case []map[string]interface{} . (Given example)

So here is the implementation I came up with. It works for most of the scenarios but not for inner Objects within an array yet.

type jsonMap map[string]interface{}
type jsonMapList []map[string]interface{}

m := jsonMap{}

err := json.Unmarshal(s, &m)
if err != nil {
    panic(err)
}

res := removeFromObject(m)

bytes, err := json.Marshal(res)
if err != nil {
    panic(err)
}
result := string(bytes)
log.Infof("Parse Result: %s", result)

func removeFromObject(in jsonMap) jsonMap {
    res := jsonMap{}

    for k, v := range in {
        switch value := v.(type) {
        case jsonMap:
            res[k] = removeFromObject(value)
        case jsonMapList:
            list := []jsonMap{}
            for _, entry := range value {
                list = append(list, removeFromObject(entry))
            }
            res[k] = list
        case []interface{}:
            if len(value) == 1 {
                res[k] = value[0]
            } else {
                res[k] = value
            }
        default:
            res[k] = value
        }
    }

    return res
}

Question

How do I switch case to an object array, so that I can recursively resolve the objects within that array too?

Answer 1

You can use this function to remove the undesired arrays.

func removearr(x interface{}) interface{} {
    switch val := x.(type) {
    case map[string]interface{}:
        for k, v := range val {
            val[k] = removearr(v)
        }
        return val
    case []interface{}:
        if len(val) == 1 {
            // remove array only if the value is not an object
            if _, ok := val[0].(map[string]interface{}); !ok {
                return removearr(val[0])
            }
        }

        for i, v := range val {
            val[i] = removearr(v)
        }
        return val
    default:
        return x
    }
}

https://play.golang.com/p/mwo7Y2rJ_lc