Re: [go-nuts] Struct with Interfaces fields as key in maps
> This works in general, but your example is flawed.
oh, my bad, thanks for the clarification
> you'll receive a runtime panic instead of a compile error.
yeah, I've received the same feedback offline from one colleague some
minutes ago ... it is a bad idea
Thanks
On Wednesday, 31 August 2022 at 16:23:57 UTC+2 bse...@computer.org wrote:
> On Wed, Aug 31, 2022 at 7:28 AM antonio.o...@gmail.com <
> antonio.o...@gmail.com> wrote:
>
>> Hi,
>>
>> Based on the documentation:
>>
>> "The map key can be any type that is comparable."
>> "Struct values are comparable if all their fields are comparable. Two
>> struct values are equal if their corresponding non-blank fields are equal."
>> "Interface values are comparable. Two interface values are equal if they
>> have identical dynamic types and equal dynamic values or if both have value
>> nil."
>>
>> My understanding is that I can use an structure like this as a key for a
>> map
>>
>> type dialer interface {
>> dial()
>> }
>>
>> type key struct {
>> id string
>> number int
>> dialer dialer
>> }
>>
>> It also seems to work fine https://go.dev/play/p/hKQfx-JH5WP
>>
>
> This works in general, but your example is flawed. In your example, you
> have
>
> f1 := {}
> f2 := {}
>
> and then use f1 anf f2 as keys. These are pointers to structs, so the
> comparison will be pointer comparison, not field-by-field comparison.
>
> If you do:
>
> f1 := fakedialer{}
> f2 := fakedialer2{}
>
> and replace the pointer receivers with value receivers, and then use these
> as map keys, it will work. But this time, if you pass a struct that cannot
> be used as a key, you'll receive a runtime panic instead of a compile error.
>
>
>> But I'm wondering if I'm missing something or are there some corner cases
>> I should take into account before doing this ... or if this is not
>> recommended at all
>>
>> Thanks,
>>
>> --
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>> "golang-nuts" group.
>> To unsubscribe from this group and stop receiving emails from it, send an
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>>
>>
>> .
>>
>
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Re: [go-nuts] Struct with Interfaces fields as key in maps
On Wed, Aug 31, 2022 at 7:28 AM antonio.o...@gmail.com <
antonio.ojea.gar...@gmail.com> wrote:
> Hi,
>
> Based on the documentation:
>
> "The map key can be any type that is comparable."
> "Struct values are comparable if all their fields are comparable. Two
> struct values are equal if their corresponding non-blank fields are equal."
> "Interface values are comparable. Two interface values are equal if they
> have identical dynamic types and equal dynamic values or if both have value
> nil."
>
> My understanding is that I can use an structure like this as a key for a
> map
>
> type dialer interface {
> dial()
> }
>
> type key struct {
> id string
> number int
> dialer dialer
> }
>
> It also seems to work fine https://go.dev/play/p/hKQfx-JH5WP
>
This works in general, but your example is flawed. In your example, you have
f1 := {}
f2 := {}
and then use f1 anf f2 as keys. These are pointers to structs, so the
comparison will be pointer comparison, not field-by-field comparison.
If you do:
f1 := fakedialer{}
f2 := fakedialer2{}
and replace the pointer receivers with value receivers, and then use these
as map keys, it will work. But this time, if you pass a struct that cannot
be used as a key, you'll receive a runtime panic instead of a compile error.
> But I'm wondering if I'm missing something or are there some corner cases
> I should take into account before doing this ... or if this is not
> recommended at all
>
> Thanks,
>
> --
> 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/97b7368e-d276-40ab-afa3-f8a7868fd9ean%40googlegroups.com
>
> .
>
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[go-nuts] Struct with Interfaces fields as key in maps
Hi,
Based on the documentation:
"The map key can be any type that is comparable."
"Struct values are comparable if all their fields are comparable. Two
struct values are equal if their corresponding non-blank fields are equal."
"Interface values are comparable. Two interface values are equal if they
have identical dynamic types and equal dynamic values or if both have value
nil."
My understanding is that I can use an structure like this as a key for a map
type dialer interface {
dial()
}
type key struct {
id string
number int
dialer dialer
}
It also seems to work fine https://go.dev/play/p/hKQfx-JH5WP
But I'm wondering if I'm missing something or are there some corner cases I
should take into account before doing this ... or if this is not
recommended at all
Thanks,
--
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