指向函数参数中的接口切片的指针

Question

I have the following function:

func read(filePath string, structure *[]interface) {
    raw, err := ioutil.ReadFile(filePath)
    if err != nil {
        fmt.Println(err.Error())
        os.Exit(1)
    }
    json.Unmarshal(raw, structure)
}

Which I call like this:

    indexes := []Index
    read(path + "/" + element + ".json", &indexes)

However, I'm getting strange error that vanish when I take off structure *[]interface from the function declaration:

./index.verb.go:73: syntax error: unexpected ), expecting {

I think something wront when I try to pass a pointer to a slice of generic type. How should I do it then? I can't do structure *[]Index because there are other types I wanna return too

Answer 1

Declare the function like this:

func read(filePath string, structure interface{}) error {
  raw, err := ioutil.ReadFile(filePath)
  if err != nil {
    return err
  }
  return json.Unmarshal(raw, structure)
}

The structure value is passed through to json.Unmarshal and can be any type supported by json.Unmarshal.

Call it like this:

var indexes []Index
err := read(path + "/" + element + ".json", &indexes)
if err != nil {
    fmt.Println(err.Error())
    os.Exit(1)
}