Go函数接受其他数组参数

Question

I want to use a generic function to unmarshal different types:

type Foo struct {
  Name    string
  Another string
}

type Bar struct {
  Name  string
  Some  string
}

func unmarshal(data []byte, val *[]map[string]interface{}) {
  err := json.Unmarshal(data, val)

  if err != nil || (*val)[0]["Name"] == "" {
    *val = nil
  }
}

func main() {
  var foos []Foo
  var bars []Bar

  // fooData and barData are JSON strings retrieved from database
  unmarshal(fooData, &foos)
  unmarshal(barData, &bars)
}

I got an error like cannot use &foo (type *[]Foo) as type *[]map[string]interface {} in argument to unmarshal.

I've tried use val interface{} as the parameter but it doesn't support index.

How can I achieve the goal then? Thanks.

Answer 1

To work with arbitrary slice types, declare the argument as type interface{} and use reflection to access the value:

func unmarshal(data []byte, v interface{}) {
    err := json.Unmarshal(data, v)
    rv := reflect.ValueOf(v).Elem()

    if err != nil || rv.Len() == 0 || rv.Index(0).FieldByName("Name").Interface() == "" {
        rv.Set(reflect.Zero(rv.Type()))
    }
}