如何处理switch case语句中返回的两个对象

Question

I'm writing type assertion helper method which accepts an interface{} and returns string along with map[string]interface{}. I'm returning both objects within a case statement. Why is it asking for return at end of function? Am i missing a break?

func typeAssertionHelper(r interface{}) (string, map[string]interface{}) {
    switch g := r.(type) {
    case string:
        return g, nil
    case []interface{}:
        for _, v := range g {
            switch s := v.(type) {
            case string:
                return s, nil
            case map[string]interface{}:
                return "", s
            }
        }
    }
    // missing return end of function
}

Answer 1

The r interface{} that's being passed in does not necessarily match one of the cases that you have in the switch block.

Essentailly the switch is not exhaustive.

You could extend the switch with a default case:

switch g := r.(type) {
 case string:
     ...
 case []interface{}:
     ...
 default:
     ...
}

Or just return something at the end of the function

return "", nil