That’s not what I mean - the function that you would be calling now (that takes
the []interface{}) would probably be generic for performance reasons, so you
wouldn’t need to do the conversion - with generics a lot of interface based
code can go away - and probably will as people chase peak performance… :(
Still, as someone opposed to generics in Go, I would love to see read-only
slices as parameters, so you could pass a []concrete to a slice of []interface
efficiently and safely (or []InterfaceA as []InterfaceB) This would more than
suffice in lieu of generics in my book...
> On Oct 31, 2018, at 10:47 AM, [email protected] wrote:
>
> It is highly likely that when go2 comes out, with generics, it will be
> trivial to write a ToInterfaceSlice() function that takes a slice of any type
> T and returns a []interface{}.
>
> On Tuesday, October 30, 2018 at 8:35:39 PM UTC-4, Justin Israel wrote:
>
>
> On Wed, Oct 31, 2018 at 1:32 PM robert engels <[email protected] <>> 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 <[email protected] <>> wrote:
>>
>>
>>
>> On Wed, Oct 31, 2018 at 11:21 AM <[email protected] <>> 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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