On Fri, Nov 25, 2022 at 12:14 AM Denis P <denis.puj...@gmail.com> wrote:
> Ok, looks like it doesn't work.
>
> I have got the following error:
> panic: interface conversion: interface {} is MyStruct, not *MyStruct
>
> So the actual code is this: https://go.dev/play/p/jBiPII7rOxG
>
> Cannot find out what is going on :-(
>
The runtime is telling you - the dynamic type of the interface is not
`MyStruct`, it is `*MyStruct`:
w := &MyWrapper{Obj: MyStruct{}}
Here, you are putting a `MyStruct` into `w.Obj`.
s := GetOf[MyStruct](&w.Obj)
You are calling `GetOf` with the address of `w.Obj`. That is, you are
passing an `*interface{}` to `GetOf[MyStruct]`. That `*interface{}` points
at an interface containing a `MyStruct` (as you just put that in).
func GetOf[T interface{}](obj *interface{}) *T {
return (*obj).(*T)
}
After instantiation, you are type-asserting the pointee of the passed
pointer to `*MyStruct`. But the value in there is a `MyStruct`. So this
panics.
I don't know how to fix your code, because I do not understand what you are
trying to do. One way to make the panic go away is to put a `*MyStruct`
into `w.Obj`:
w := &MyWrapper{Obj: &MyStruct{}}
(note the second `&`). Another would be, to not type-assert on a `*T`, but
a `T` and return a pointer pointing at the same value:
x := (*obj).(T)
return &x
You also probably do not want to take a `*interface{}`, but just take the
interface directly… So maybe you want this?
https://go.dev/play/p/5w-sMtVyTE3
The code isn't particularly functional, so I have no idea what the intended
fix is. But the compiler and runtime are telling you, what you are doing
wrong, in either case.
>
> On Thursday, 24 November 2022 at 22:29:21 UTC axel.wa...@googlemail.com
> wrote:
>
>> Hi,
>>
>>
>> On Thu, Nov 24, 2022 at 11:16 PM Denis P <denis....@gmail.com> wrote:
>>
>>> Hi guys, tried to look everywhere and cannot find an answer.
>>>
>>> So literally I have this:
>>> ```
>>> var result interface{} = &MyStruct{}
>>>
>>> ...
>>>
>>> return result.(*MyStruct) // Error: invalid operation: result
>>> (variable of type *interface{}) is not an interface
>>> ```
>>>
>>
>> No, offense, but you literally do not have that code, because the error
>> message does not fit that code. In your code, `result` has type
>> `interface{}`, whereas in the `return` statement, according to the error
>> message, it has type `*interface{}`. Ergo, you are either shadowing
>> `result` in-between, or the code is not equivalent.
>>
>> In any case, the immediate solution could be to dereference the pointer:
>> return (*result).(*MyStruct)
>>
>>
>>>
>>> Is there any way to get the &MyStruct as a result?
>>>
>>> --
>>> 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/25da3c8f-6126-439a-904a-5fec59cb09f4n%40googlegroups.com
>>> <https://groups.google.com/d/msgid/golang-nuts/25da3c8f-6126-439a-904a-5fec59cb09f4n%40googlegroups.com?utm_medium=email&utm_source=footer>
>>> .
>>>
>> --
> 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+unsubscr...@googlegroups.com.
> To view this discussion on the web visit
> https://groups.google.com/d/msgid/golang-nuts/d1a148b6-99f1-47fa-9c4a-4c8823fb15acn%40googlegroups.com
> <https://groups.google.com/d/msgid/golang-nuts/d1a148b6-99f1-47fa-9c4a-4c8823fb15acn%40googlegroups.com?utm_medium=email&utm_source=footer>
> .
>
--
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+unsubscr...@googlegroups.com.
To view this discussion on the web visit
https://groups.google.com/d/msgid/golang-nuts/CAEkBMfE3A7HOMvRmYTmB6xxyCk3yo%3D5LbEkHSfxeTFwNbV8pMw%40mail.gmail.com.
