golang: How to check for exported fields in an interface

Question

short version:

 import ( "fmt" "reflect" ) type StatusVal int type Foo struct { Name string Age int art string } func ListFields(a interface{}) { v := reflect.ValueOf(a).Elem() fmt.Printf(" Kind: %+v \n", v.Type()) for _, f := range reflect.VisibleFields(v.Type()) { if f.IsExported() { fmt.Printf(" Kind: %+v \n", f) } else { fmt.Printf(" Kind: %s \n", f.Name) } } } func main() { var x Foo ListFields(&x) }

This code works, but what I really need is var x []Foo , and I cannot find a way to get that to work and check for IsExported in the fields of the slice of structs.

Long version:

I was looking to generate a generic sqlToStruct function, and I bumped into this awesome answer: Generalizing *sql.Rows Scan in Go

I don't have the reputation to reply there.

The only problem with that is that if my struct has any unexported fields, it panics, and I would like to check for that and return an error to be handled, rather than let it panic.

Also: I have been coding in go for a very short amount of time, please understand where I am coming from and sorry if I am missing something absolutely obvious.

if you'd like to provide an official answer I can upvote that :) — Fabri Ba
– Fabri Ba, Commented Feb 11, 2022 at 11:43

mkopriva · Accepted Answer · 2022-02-11 11:49:45Z

func ListFields(a interface{}) { rt := reflect.TypeOf(a) // take type of a if rt.Kind() == reflect.Ptr { rt = rt.Elem() // use Elem to get the pointed-to-type } if rt.Kind() == reflect.Slice { rt = rt.Elem() // use Elem to get type of slice's element } if rt.Kind() == reflect.Ptr { // handle input of type like []*StructType rt = rt.Elem() // use Elem to get the pointed-to-type } if rt.Kind() != reflect.Struct { return } fmt.Printf(" Kind: %+v \n", rt) for _, f := range reflect.VisibleFields(rt) { if f.IsExported() { fmt.Printf(" Kind: %+v \n", f) } else { fmt.Printf(" Kind: %s \n", f.Name) } } }

https://go.dev/play/p/0J3VXmFPe87

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