On Wed, Oct 31, 2018 at 1:32 PM robert engels <reng...@ix.netcom.com> wrote:
> I have argued for a runtime/built-in to do this - it is so common…. (if
> doing “kind of OO” in Go)
>
I would love to have the ability to do it with built-in support, but I feel
like it would go against the goals of not wanting to hide complexity. It
wouldn't be "free" to do it (as far as I know) and I doubt the Go
maintainers want it to hide the copy into the new slice. My 2 cents.
>
>
> On Oct 30, 2018, at 7:30 PM, Justin Israel <justinisr...@gmail.com> wrote:
>
>
>
> On Wed, Oct 31, 2018 at 11:21 AM <zloikom...@gmail.com> wrote:
>
>> Hello, everyone.
>> Consider following code:
>>
>> package main
>> import "fmt"
>>
>> type implementation struct {
>> d []int}
>>
>> func (impl *implementation) getData() interface{} {
>> return impl.d}
>>
>> type phase struct{}
>>
>> type data interface {
>> getData() interface{}}
>>
>> func MakeIntDataPhase() *phase {
>> return &phase{}}
>>
>> func (p *phase) run(population []data) []data {
>> return nil}
>>
>> func main() {
>> var population []implementation
>> MyPhase := MakeIntDataPhase()
>> fmt.Println(MyPhase.run(population))
>> }
>>
>>
>> When running following code in playground I got following error:
>> prog.go:30:25: cannot use population (type []implementation) as type []data
>> in argument to MyPhase.run
>>
>> If I understand correctly it is because slice of interface type cannot be
>> converted by the compiler to concrete type.
>>
>>
>> What is correct way in golang to implement functionality that is presented
>> in the example?
>>
>> When method argument defined using a slice of some interface, how I can pass
>> it a slice of a concrete type that implements the interface?
>>
>>
> You would end up needing to just do
>
> func (p *phase) run(population {}interface) []data
>
> and then type assert the {}interface into []implementation
> There isn't a way to directly pass a slice of concrete type to a function
> that accepts a slice of interface, unless you first do this:
>
> iface := make([]data, len(population))
> for i, p := range population {
> iface[i] = p
> }
> MyPhase.run(iface)
>
> Justin
>
>>
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