To be clear what I mean with "not particularly functional": Your GetOf is
just doing a type-assertion, so the right way to write it would be this:
https://go.dev/play/p/hTqOCbc07-K
You must have a reason to go through the more complicated dance of your
GetOf function, but without knowing that, it's hard to tell what exactly
the misunderstanding or the best solution is.
On Fri, Nov 25, 2022 at 7:11 AM Axel Wagner <axel.wagner...@googlemail.com>
wrote:
>
>
> 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/CAEkBMfF7CxL7twy7GqkzZ0M_3QiUnmMVqRvnFir1TCSqV4dwEw%40mail.gmail.com.
