On Monday, 7 November 2016 17:55:57 UTC-5, Kaylen Wheeler wrote:
>
> I'm trying to find a typesafe way to access a type-indexed map of
> components. This map can contain objects of any type, and the keys are
> reflect.Type.
>
> One strategy I thought may work would be to pass a pointer to a pointer as
> an out-var. Using reflection to determine the pointer's type, it could be
> populated with a corresponding value.
>
> For instance, if we did something like this:
>
> c := ComponentCollection{}
> c.addComponent(123) // Add an int component
>
> var p : *int
> c.getComponent(&p)
>
>
> In this case, p would point to the int component of c.
>
> That's wht the 2 levels of indirection are necessary: it's an out-var to a
> pointer.
>
> Does that make sense?
>
Here's the basic pattern:
var m = make(map[reflect.Type]reflect.Value)
func addComponent(x interface{}) {
v := reflect.ValueOf(x)
m[v.Type(x)] = v
}
func getComponent(ptr interface{}) {
rv := reflect.ValueOf(ptr)
if rv.Kind() != reflect.Pointer {
panic("not a pointer")
}
rv.Elem().Set(m[rv.Type()])
}
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