// A use case to avoid:: panic: reflect.Value.Interface: cannot return
value obtained from unexported field or method
```
package main
import (
"fmt"
"reflect"
"strings"
"unsafe"
)
type Person1 struct {
W3ID string
Name string
}
type Address1 struct {
city string
country string
}
type User1 struct {
name string
age int
address Address1
manager Person1
developer Person1
tech Person1
}
func showDetails(load, email interface{}) {
//fmt.Println("The values in the first argument are :")
if reflect.ValueOf(load).Kind() == reflect.Struct {
typ := reflect.TypeOf(load)
value := reflect.ValueOf(load)
value2 := reflect.New(value.Type()).Elem() // #1 For struct, not
addressable create a copy With Elements.
value2.Set(value) //#2 Value2 is
addressable and can be set
for i := 0; i < typ.NumField(); i++ {
//fmt.Println(value.Field(i).Kind(), "---------")
if value.Field(i).Kind() == reflect.Struct {
rf := value2.Field(i)
rf = reflect.NewAt(rf.Type(),
unsafe.Pointer(rf.UnsafeAddr())).Elem()
irf := rf.Interface()
typrf := reflect.TypeOf(irf)
nameP := typrf.String()
if strings.Contains(nameP, "Person") {
//fmt.Println(nameP, "FOUND !!!!!!! ")
for j := 0; j < typrf.NumField(); j++ {
//fmt.Println(j)
re := rf.Field(j)
nameW := typrf.Field(j).Name
//fmt.Println(nameW)
if strings.Contains(nameW, "W3ID") {
//fmt.Println(nameW)
valueW := re.Interface()
fetchEmail := valueW.(string)
//fmt.Println(fetchEmail)
if fetchEmail == email {
fmt.Println(fetchEmail, " MATCH!!!!")
}
}
}
}
//fmt.Println(rf.Interface(), "++=====")
showDetails(irf, email)
} else {
// fmt.Printf("%d.Type:%T || Value:%#v\n",
// (i + 1), value.Field(i), value.Field(i))
// fmt.Println("Kind is ", value.Field(i).Kind())
}
}
}
}
func main() {
iD := "ts...@in.org.com"
load := User1{
name: "John Doe",
age: 34,
address: Address1{
city: "New York",
country: "USA",
},
manager: Person1{
W3ID: "jb...@in.org.com",
Name: "Bualt",
},
developer: Person1{
W3ID: "ts...@in.org.com",
Name: "Sumi",
},
tech: Person1{
W3ID: "lp...@in.org.com",
Name: "Paul",
},
}
showDetails(load, iD)
}
```
On Tuesday, February 11, 2020 at 7:17:48 PM UTC+5:30 rog wrote:
> On Tue, 11 Feb 2020 at 03:38, Ian Lance Taylor <ia...@golang.org> wrote:
>
>> On Mon, Feb 10, 2020 at 4:15 AM 'Axel Wagner' via golang-nuts
>> <golan...@googlegroups.com> wrote:
>> >
>> > It's reflect, so I don't feel confident in making any absolute
>> statements (we've talked about it a bunch; I just find the implications of
>> that API far too unwieldy to handle), but I tend to agree. You need a
>> reference value and Bytes() seems the only typed reference value you can
>> get out of reflect.Value without using Interface() and type-assertion. I
>> don't think this can be fixed either - not just because of compatibility,
>> but also because it would impede fmt.Print*.
>>
>> https://golang.org/issue/27727.
>>
>
> Ah, thanks! I'd missed that. I added a comment there FWIW.
>
>
>>
>> Ian
>>
>> > On Mon, Feb 10, 2020 at 11:46 AM roger peppe <rogp...@gmail.com> wrote:
>> >>
>> >> On Sun, 9 Feb 2020 at 00:19, 'Axel Wagner' via golang-nuts <
>> golan...@googlegroups.com> wrote:
>> >>>
>> >>> (then again, the fact that this works seems slightly concerning to
>> me: https://play.golang.org/p/phWQ83wPQtx)
>> >>
>> >>
>> >> Oh, that's interesting! Is this the only way that you can use reflect
>> (without unsafe) to modify the contents of unexported fields?
>> >> I think it might be.
>> >>
>> > --
>> > You received this message because you are subscribed to the Google
>> Groups "golang-nuts" group.
>> > To unsubscribe from this group and stop receiving emails from it, send
>> an email to golang-nuts...@googlegroups.com.
>> > To view this discussion on the web visit
>> https://groups.google.com/d/msgid/golang-nuts/CAEkBMfG%3Di%2BPgKBfsNPtWNZXMzQV2AAqk%3DnQuo7Oi_pabXcJQEA%40mail.gmail.com
>> .
>>
>
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