On Nov 12, 3:21 am, Wardrop <[email protected]> wrote:
> Here's the scenario. I have a 'post' table (I've chosen not to use
> pluralization), and a 'postmeta' table. The 'post' table stores the
> main post information, such as title, body and date_created. The
> 'postmeta' table stores metadata associated with the post, such as
> tags, and the post type (e.g. whether the post is an article or a blog
> entry).
>
> I've created models for both the post and postmeta tables, like so...
>
> class Postmeta < Sequel::Model
> many_to_one :post
> end
>
> class Post < Sequel::Model
> one_to_many :postmeta
> end
>
> The association works fine, I can assure you. My problem is, I can't
> for the life of me, work out how to select all posts with the 'type'
> of 'blog'. Of course, the 'type' information is stored in the
> 'postmeta' table, so here's how I'd write that in pure SQL...
>
> SELECT * FROM post
> JOIN postmeta ON postmeta.post_id = post.id
> WHERE postmeta.name = 'type' AND postmeta.value = 'blog'
This query would not be generated by any association code, since it is
not specific to a particular post or postmeta.
To do filtering on associations, you can use :conditions (or a block).
Post.one_to_many :postmeta, :conditions=>{:name=>'type', :value =>
'blog'}
My guess is you really want this to be a dataset method on Post:
Post.def_dataset_method(:blogs) do
join(:postmeta, :post_id=>:id).
filter(:postmeta__name=>'type',
:postmeta__value=>'blog')
end
This would allow you to do this to get all posts that are blogs:
Post.blogs
Jeremy
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