I want pointers because I want most components to be structs, and I want
the ability to modify the fields in those structs.
On Monday, 7 November 2016 16:46:17 UTC-8, freeformz wrote:
>
> Why do you want to use pointers?
>
> On Mon, Nov 7, 2016 at 4:42 PM Kaylen Wheeler <kfjwh...@gmail.com
> <javascript:>> wrote:
>
>> Thanks for the "basic pattern" example here. There's one little
>> modification I'm wondering about.
>>
>> Can this line:
>>
>> rv.Elem().Set(m[rv.Type()])
>>
>> be changed to this?
>>
>> rv.Elem().Set(*&*m[rv.Type()])
>>
>> If so, how can we check that the input value is a pointer to a pointer.
>>
>> Or alternatively, is it better that the values in m should be pointers?
>>
>>
>> On Monday, 7 November 2016 16:01:53 UTC-8, adon...@google.com wrote:
>>>
>>> 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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