Creating a struct with dynamic field names

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1

I’m having the below code that is creating a struct using reflection:

package main

import (
	"fmt"
	"reflect"
)

func main() {
	name := "Myfield"
	age := 25
	t := reflect.StructOf([]reflect.StructField{
		{
			Name: reflect.ValueOf(name).Interface().(string),
			Type: reflect.TypeOf(age),
			Tag:  `json:"name"`,
		},
	})

	v := reflect.New(t)
	e := v.Elem()
	e.Field(0).SetInt(1234)
	d := e.Addr().Interface()

	fmt.Printf("value: %+#v\n", d)

}

I need to add other fields to this struct based on some definistion in other place, let’s say something like:

	fields := []string{"area", "size"}
	types := []interface{}{5, 10.3}
	for i, v := range fields {
		x := reflect.StructField{
			Name: reflect.ValueOf(v).Interface().(string),
			Type: reflect.TypeOf(types[i]),
		}

		t = append(t, x)
	}

But the t = append(t, x) looks to be wrong, how can I add the fileds defined in the range over the slices to the []reflect.StructField of the struct t

2

t is a struct not a slice, so it should be declared as :
t:= make([]interface{}, 0)

3

I was able to do it as:

package main

import (
	"reflect"
)

func CreateStruct() reflect.Value {
	f := []reflect.StructField{}
	fields := []string{"Myfield", "Area", "Size"}
	types := []interface{}{25, 5, 10.3}

	for i, v := range fields {
		x := reflect.StructField{
			Name: reflect.ValueOf(v).Interface().(string),
			Type: reflect.TypeOf(types[i]),
		}

		f = append(f, x)
	}

	t := reflect.StructOf(f)

	e := reflect.New(t).Elem()

	return e
}

And call and manipulate it as:

func main() {
	e := CreateStruct() // reflect.Value
	e.FieldByName("Area").SetInt(1234)
	fmt.Printf("value: %+#v\n", e)
	fmt.Printf("value: %+#v %+#v\n", e.FieldByName("Myfield"), e.FieldByName("Area"))

	s := e.Addr().Interface()

	w := new(bytes.Buffer)
	if err := json.NewEncoder(w).Encode(s); err != nil {
		panic(err)
	}

	fmt.Printf("value: %+v\n", s)
	fmt.Printf("json:  %s", w.Bytes())

	rx := bytes.NewReader([]byte(`{"Myfield":0,"Area":1234,"Size":20}`))
	if err := json.NewDecoder(rx).Decode(s); err != nil {
		panic(err)
	}
	fmt.Printf("value: %+v\n", s)
}

The output of teh above is:
```bash
value: struct { Myfield int; Area int; Size float64 }{Myfield:0, Area:1234, Size:0}
value: 0 1234
value: &{Myfield:0 Area:1234 Size:0}
json:  {"Myfield":0,"Area":1234,"Size":0}
value: &{Myfield:0 Area:1234 Size:20}