I have a situation where I would like to create a type, then set a property
on it within a container. To set the type, I envisioned using a method
"SetName" which would need to take a pointer receiver: (goplay share is
down right now so I'll post inline:
type Namer interface {
SetName(name string)
}
I wish to create a new Namer type as well, ideally without using reflect.
If I use [*Ob ] as the type parameter, that works, but then `new(T)`
returns `**Ob`, which I can deference to get `*Ob`, but then the value is
nil (Ob isn't created).
I'm working around this, but it surprised me, the interaction of a pointer
receiver interface type constraint and then I can't create the desired type.
```
package main
import "fmt"
func main() {
ar := NewAppResult()
fmt.Printf("AR: %#v\n", *ar)
ar.Observation.Get("X1")
}
type Ob struct {
Gene string
Value string
}
func (o *Ob) SetName(name string) {
// o is nil and this will panic.
o.Gene = name
}
type Namer interface {
SetName(name string)
}
type OrderedLookup[T Namer] struct {
List []T
lookup map[string]T
}
func (ol *OrderedLookup[T]) Get(name string) T {
v, ok := ol.lookup[name]
if !ok {
var v T // T is a pointer, new(T) creates **Ob, but I cant use generic type
of [Ob] because then Namer
v.SetName(name)
ol.lookup[name] = v
ol.List = append(ol.List, v)
}
return v
}
type AppResult struct {
Observation *OrderedLookup[*Ob]
}
func NewAppResult() *AppResult {
return &AppResult{
Observation: &OrderedLookup[*Ob]{},
}
}
```
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