Get name of struct field using reflection

Question

What is the way of printing "Foo" here? In this example, what prints is "string".

http://play.golang.org/p/ZnK6PRwEPp

type A struct {
    Foo string
}

func (a *A) PrintFoo() {
    fmt.Println("Foo value is " + a.Foo)
}

func main() {
    a := &A{Foo: "afoo"}
    val := reflect.Indirect(reflect.ValueOf(a))
    fmt.Println(val.Field(0).Type().Name())
}

Answer 1

You want val.Type().Field(0).Name. The Field method on reflect.Type will return a struct describing that field, which includes the name, among other information.

There is no way to retrieve the field name for a reflect.Value representing a particular field value, since that is a property of the containing struct.

Answer 2

You need to Get the Field of the Type Definition not of the Value.

http://play.golang.org/p/7Bc7MJikbJ

package main

import "fmt"
import "reflect"

type A struct {
    Foo string
}

func (a *A) PrintFoo() {
    fmt.Println("Foo value is " + a.Foo)
}

func main() {
    a := &A{Foo: "afoo"}
    val := reflect.Indirect(reflect.ValueOf(a))
    fmt.Println(val.Type().Field(0).Name)
}

Answer 3

I think the better way to get the fields' name in the struct is

func main() {
    a := &A{Foo: "afoo"}
    val := reflect.ValueOf(a).Elem()
    for i:=0; i<val.NumField();i++{
        fmt.Println(val.Type().Field(i).Name)
    }
}

There are two tips:

1. use .Elem() after you reflect.ValueOf(a), because in your case, a is a pointer.
2. val.Field(i).Type().Name is totally different from val.Type().Field(i).Name. The latter one can get the name of the field in the struct

Hope that it is helpful..

If you want to have a look at more cases, please check my 2mins article

Answer 4

With the new Names method of the structs package it's even more easier:

package main

import (
    "fmt"

    "github.com/fatih/structs"
)

type A struct {
    Foo string
    Bar int
}

func main() {
    names := structs.Names(&A{})
    fmt.Println(names) // ["Foo", "Bar"]
}

Answer 5

You can also use https://github.com/fatih/structs

// Convert the fields of a struct to a []*Field
fields := s.Fields()

for _, f := range fields {
    fmt.Printf("field name: %+v\n", f.Name())
}