Thanks a lot!
在 2017年4月30日星期日 UTC+8下午1:45:26，T L写道：
>
>
>
> On Sunday, April 30, 2017 at 10:54:07 AM UTC+8, feilengcui008 wrote:
>>
>> So, if i do this:
>> //assign some var to interface type
>> var i io.Reader = readerImpl
>> i.Read(buf)
>>
>> the interface i's dynamic type infomation is filled by type deduction in
>> compiling phase?
>>
>
> yes
>
>
>>
>> also the function table in itab field of interface implementation filling
>> with the actually methods of readerImpl also happened in compiling phase?
>>
>
> compiler can, but this is done at run time.
>
>
>>
>> if so, this is kind of similar with C++ virtual functions?
>>
>
> yes, I think so.
>
>
>>
>>
>> 在 2017年4月30日星期日 UTC+8上午3:23:54，T L写道：
>>>
>>>
>>>
>>> On Saturday, April 29, 2017 at 9:56:20 PM UTC+8, feilengcui008 wrote:
>>>>
>>>> Hey, All
>>>>
>>>> I'm curious about what happened when map or slice is assigned to
>>>> interface variables.
>>>>
>>>> I know the interface implementation in go runtime is:
>>>> type iface struct{
>>>> tab *itab
>>>> data unsafe.Pointer
>>>> }
>>>> and the interface static and dynamic type infomation are stored in
>>>> itab, when we use reflect.TypeOf or reflect.ValueOf,
>>>> we can get the dynamic type infomation of this interface.
>>>>
>>>> But it seems that the implementations of slice or map do not have the
>>>> underline element type infomation, here is the map implementation:
>>>> // A header for a Go map.
>>>> type hmap struct {
>>>> count int // # live cells == size of map. Must be first (used by
>>>> len() builtin)
>>>> flags uint8
>>>> B uint8 // log_2 of # of buckets (can hold up to loadFactor *
>>>> 2^B items)
>>>> noverflow uint16 // approximate number of overflow buckets; see
>>>> incrnoverflow for details
>>>> hash0 uint32 // hash seed
>>>>
>>>> buckets unsafe.Pointer // array of 2^B Buckets. may be nil if
>>>> count==0.
>>>> oldbuckets unsafe.Pointer // previous bucket array of half the size,
>>>> non-nil only when growing
>>>> nevacuate uintptr // progress counter for evacuation (buckets
>>>> less than this have been evacuated)
>>>> overflow *[2]*[]*bmap
>>>> }
>>>>
>>>> So when we use reflect.TypeOf or reflect.ValueOf, the map variable will
>>>> be transformed to interface{} and the empty interface will contains the
>>>> type information of the map, how does this happen? where does the
>>>> interface{} get the type information?
>>>>
>>>
>>> compiler knows what type the map/slice is.
>>>
>>>
>>>>
>>>>
>>>> Thanks in advance.
>>>>
>>>
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