Thanks guys. I have finished my homework thanks to you: https://pkg.go.dev/github.com/fairking/di_plus
On Friday, 25 November 2022 at 16:35:50 UTC pattnaik...@gmail.com wrote: > If you create a wrapper interface type and create *generic constraints* with > the *MyWrapper* struct then it'll type cast with *interface* with *(T)*. > > https://go.dev/play/p/-VnQxG77sDL > > > On Fri, Nov 25, 2022 at 3:38 PM 'Axel Wagner' via golang-nuts < > golan...@googlegroups.com> wrote: > >> If you assign a value to an interface, it will get copied. That's the >> same as if you assign an int to another int - it will get copied. If you >> want the interface to contain a reference, you have to assign a pointer to >> it: https://go.dev/play/p/nLw51pjWh4u >> >> Side note: Go doesn't have "instances". It has "variables", which is >> *probably* what you mean. >> >> On Fri, Nov 25, 2022 at 10:55 AM Denis P <denis....@gmail.com> wrote: >> >>> Thank you everyone for your help. >>> The problem still exists. >>> I am looking for a solution where s and s2 point to the same instance. >>> The current example proves they are different instances. >>> https://go.dev/play/p/_JyfJelhIy4 >>> >>> The main goal is to store any type in a wrapper and then get the >>> reference of the actual struct. >>> Also it must be the same instance, so the println should print 2, 2, 2 >>> >>> But look like there is no obvious solution. :-( >>> >>> On Friday, 25 November 2022 at 08:19:17 UTC Brian Candler wrote: >>> >>>> To give a real-world example: >>>> >>>> https://pkg.go.dev/github.com/prometheus/client_golang/prometheus >>>> >>>> type metrics struct { >>>> cpuTemp prometheus.Gauge >>>> hdFailures *prometheus.CounterVec >>>> } >>>> >>>> Question: why is prometheus.Gauge not a pointer, but >>>> *prometheus.CounterVec is a pointer? >>>> >>>> Answer: because prometheus.Gauge is an interface, whereas >>>> prometheus.CounterVec is a struct. >>>> >>>> An interface essentially already *contains* a pointer to a data value - >>>> in fact, a tuple of (type, pointer). So you should never take a pointer >>>> to >>>> an interface. Just pass the interface value, and it will copy the (type, >>>> pointer) pair. >>>> >>>> However, when you extract a value from an interface, it *will* always >>>> copy the internal value. This avoids aliasing issues: someone who passes >>>> an interface value to someone else, won't expect the recipient to be able >>>> to change the sender's copy. >>>> >>>> e.g. >>>> https://go.dev/play/p/u5y3Kwm9Ydz >>>> >>>> Of course, if your interface *contains* a pointer, then the recipient >>>> of the interface can modify the thing being pointed to. >>>> https://go.dev/play/p/o_XAJtNuyGF >>>> >>>> But they can't modify the pointer itself held within the interface, to >>>> make it point to something else. >>>> >>>> The short version is: avoid pointers to interfaces, as the FAQ says. >>>> Instead, let a concrete pointer value satisfy an interface. >>>> >>>> On Friday, 25 November 2022 at 07:40:59 UTC Nigel Tao wrote: >>>> >>>>> Possibly relevant: >>>>> https://go.dev/doc/faq#pointer_to_interface >>>>> >>>> -- >>> 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/948dc8f3-385e-4f50-a44b-ddf4792e6362n%40googlegroups.com >>> >>> <https://groups.google.com/d/msgid/golang-nuts/948dc8f3-385e-4f50-a44b-ddf4792e6362n%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...@googlegroups.com. >> > To view this discussion on the web visit >> https://groups.google.com/d/msgid/golang-nuts/CAEkBMfE7XX%2BnHJTW36GaoLjQWidY7GCjpHP1zyOJJzMcSq13JA%40mail.gmail.com >> >> <https://groups.google.com/d/msgid/golang-nuts/CAEkBMfE7XX%2BnHJTW36GaoLjQWidY7GCjpHP1zyOJJzMcSq13JA%40mail.gmail.com?utm_medium=email&utm_source=footer> >> . >> > > > -- > > > Thanks & Regards > Deeptiman Pattnaik > -- 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/b09312e7-c52e-4517-bed1-1ff0352cabf5n%40googlegroups.com.
