On Jul 7, 6:22 pm, Alexander Dergachev <[email protected]> wrote:
> OK, I guess, now I understand what you meant. You're going to create tree
> structure for your forum, and you're going to create "sub-sub-forum", aren't
> you? And as I understood, you were trying to use the same table for the all
> sub forums, weren't you? I guess it's impossible, and my suggestion is to
> create separate tables for every "layer" of your forum tree (main forum
> (table1) -> sub-forum layer 1 (table2) -> sub-forum layer 2 (table2) and so
> on).
>
> If somebody knows any other ways for this purpose, it would be good to see.
>
> Thanks.
>
> /Regards,
> Alexander
>
> On Tue, Jul 7, 2009 at 8:27 PM, Alexander Dergachev
> <[email protected]>wrote:
>
>
>
> > I'm not quite sure I understood you right. Where are you going to use it?
>
> > relation()->
> > [{many_to_one, [forum]},{one_to_many, [forum]}].
>
> > Where do you need to use it?
>
> > May be it would be more easy to help you if you show some code
> > examples you're going to use in your application.
>
> > On 7/7/09, Hao Chi Kiang <[email protected]> wrote:
>
> > > 2009/7/7 Alexander Dergachev <[email protected]>
>
> > >> Hi. If I got it right, then I don't see any problem :)
>
> > >> As I understood the concept of subforums, any forum can have some
> > >> number of subforums, but is it really case one subforum may be placed
> > >> in more them one forum? Do we really need many-to-many relation?
>
> > >> On 7/7/09, Takayoshi Kyou <[email protected]> wrote:
>
> > >> > Hi all,
>
> > >> > I am trying to make a forum application that every forum can have
> > >> > their
> > >> > child-forums. But I found it hard to represent these with erlydb.
>
> > >> > First I tried to use a self-referencing many-to-many relation:
>
> > >> > new (A) ->
> > >> > Post_data = yaws_api:parse_post(A),
> > >> > {value, {parent_forum_id, Parent_forum_id_str}, Other_fields} =
> > >> > lists:keytake(parent_forum_id, 1,
> > >> > %% convert every keys from string to atom
> > >> > [ {list_to_atom(K), V} || {K, V} <- Post_data ]),
> > >> > New_forum = forum:save(forum:new_with(Other_fields)),
> > >> > Parent_forum_id = list_to_integer(Parent_forum_id_str),
> > >> > %% A negative parent ID means it is an orphan.
> > >> > if Parent_forum_id > 0 ->
> > >> > forum:add_forum( forum:find_id(Parent_forum_id), New_forum
> > );
> > >> > true ->
> > >> > ok
> > >> > end,
> > >> > {ewr, forum, index}.
>
> > >> > But this isn't work because the relation between parent and child is
> > >> > "two-way"
> > >> > that I can't detect who is the parent and who are the childern when I
> > >> > use
> > >> > forum:forums to access it.
>
> > >> > Any idea?
>
> > >> > Thanks
>
> > >> --
> > >> With Best Regards,
> > >> Alexander Dergachev
>
> > > Oh. Maybe I'm going the wrong way...
> > > Yes, this is only a one-to-many relations that one forum can have many
> > > sub-forums. Is it means I should define a "self-referencing one-to-many
> > > relation"?
>
> > > But maybe why I think of many-to-many first is that I felt unnatural to
> > > write a
> > > self-referencing one-to-many relation.
>
> > > If table1 have a one-to-many relation to table2, I would say:
>
> > > -module(table1).
> > > relations () -> {one_to_many, [table2]}.
>
> > > -module(table2).
> > > relations () -> {many_to_one, [table1]}.
>
> > > But it's strange to say:
> > > relations () -> [{one_to_many, [forum]}, {many_to_one, [forum]}].
>
> > > Or maybe I should just use a extra column called parent_forum_id? If I do
> > > so,
> > > will it going to be inconvenient to access them (because erlydb won't
> > make
> > > access functions automatically)?
>
> > > Thanks.
>
> > --
> > With Best Regards,
> > Alexander Dergachev
>
> --
> With Best Regards,
> Alexander Dergachev
Yes, that's what I mean. And sorry for my bad English.
Well, I'll try your suggestion. Thanks again.
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