Re: [boost] Checking interest: reflectable types

Subject: Re: [boost] Checking interest: reflectable types
From: Larry Evans (cppljevans_at_[hidden])
Date: 2011-04-27 16:06:15

On 04/27/11 13:53, Noah Roberts wrote:
> On 4/27/2011 10:42 AM, Matus Chochlik wrote:
[snip]
>
>> There is also the Mirror reflection library which I plan to
>> submit for review once it is ready.
>>
>> The project homepage (with links to docs and download page)
>> is located here http://kifri.fri.uniza.sk/~chochlik/mirror-lib/html/
>
> Yeah, the original worked like that.  We found the manual registration
> process ungainly.  Also didn't do proper inheritance...which maybe
> yours does.  Had trouble looking at the docs and seeing how to use it
> since the part that probably does all the work (classes.h) isn't
> linked in with the examples.
Hi, Noah,

Sounds interesting. I'd be interested in seeing the code.

>
> Use of mine is more like so:
>
> struct field0 { typedef int value_type; };
> struct field1...2 ...
>
> struct my_reflected_type
>   : build_class
>     <
>       var< field0, rw >
>     , var< field1, r > // can't assign through reflection.
Why not:

          var< field >
        , var< field const>

instead?  I guess I'd have to see the code to really
understand why the extra type parameter is needed,
but maybe a short explanation would be enough.

>     >::type
> {
>   virtual ~my_reflected_type(){}
>   DECLARE_PARAM_CONSTRUCTOR(my_reflected_type);
Could you provide the source code for:

  DECLARE_PARAM_CONSTRUCTOR

to give us some idea of what it's doing?
> };
>
> struct my_reflected_type2
>   : derive_from
>     <
>       my_reflected_type
>     , var< field2, rw >
>     >::type
> {
>   my_reflected_type2()
>     : type(( field0() <= some_val
>            , field1() <= some_val
>            , field2() <= some_val ))
>   {
>     // directly access read-only value and assign...
>     var<field1,r>::value = 66.;
>   }
> };

Hmm... does the user have to repeat this some number of
times, same the number of fields in the my_reflected_type?
IOW, for I=3...N (where N is number of fields in my_reflected_type):

  my_reflected_typeI
  {
  //repeat like my_reflected_type2
  };

Or is this done by the macro using boost,preprocessor library?
I would guess the latter because providing all this boilerplate
code would seem too much to me.

>
> I also have a ref<> so bases can have fields to abstract types.
>
> So far functions haven't been needed here so there's none but I think
> I have a handle on how that could be done.
>
> All of the above can be treated as a fusion sequence and/or fusion
> associative sequence (including the param list).
>
> Building records on the fly with field()<=value syntax was very
> desired.  Comes in handy when you have a function expecting a record
> with x,y,z fields in it, have those values, but don't want to build
> the record class.
I don't understand that.  Could you be more concrete in describing
this use case, maybe by providing a concrete example?

----------------------------
BTW, a previous post of your's to the users list:

  http://thread.gmane.org/gmane.comp.lib.boost.user/66818/focus=67038

seems related to your:

  field()<=value

syntax.  Is it?

-regards,
Larry