动态创建某种类型的结构并将其解编成JSON

Question

I am creating a struct instance at runtime. The instance has been created successfully, but I can't unmarshal JSON into it.

type Test struct {
    Name string `json:"name,omitempty"`
}

func create(a interface{}) {
    aType := reflect.TypeOf(a).Elem()
    elType := aType.Elem()

    f := reflect.Indirect(reflect.New(elType))

    b := []byte(`{"name": "go"}`)

    err := json.Unmarshal(b, &f)
    fmt.Println(err, f)
}

func main() {
    l := []Test{}
    create(&l)
}

Answer 1

reflect.Indirect() returns you a value of type reflect.Value, and you should pass a pointer to Test (which is of type *Test) to json.Unmarshal().

Simply use the Value.Interface() method to obtain the pointer to your Test struct returned by reflect.New(), like this:

f := reflect.New(elType).Interface()
b := []byte(`{"name": "go"}`)
err := json.Unmarshal(b, f)

With this it works, and output will be:

<nil> &{go}

Note that f will be of interface{} type, holding the *Test pointer value. If you need the struct value, you may use type assertion, like this:

t := *f.(*Test)
fmt.Println(t)

This prints:

{go}

Try the examples on the Go Playground.