将元帅提升为结构

Question

I have two structs. One inherits from the other.

type Animal struct {
    Name string `json:"name"`
}

type Dog struct {
    Animal
    Color string `json:"color"`
}

When I go to Unmarshal to Dog by passing in:

{
  "name": "Loki",
  "color": "Brown"
}

I'm getting an *encoding/json.InvalidUnmarshalError. 2019/03/10 00:22:35 json: Unmarshal(nil *main.Dog)

Why is that?

Here's the unmarshal code:

func main() {
    var dog *Dog

    err := json.Unmarshal([]byte(`{
        "name": "Loki",
        "color": "Brown"
    }`), dog)

    if err != nil {
        log.Fatal(err)
    }
}

Answer 1

That's because the variable dog is nil. Try to initialize it to point to an empty Dog. Or make it a Dog instead of a pointer to Dog and pass in the address to Unmarshal.