hi all -
i’ve got roughly the following from a legacy db (so no suggestions of
changing schema)
a class which models a peice a web content
class WebContent
# web_contentid | content
end
a join table which maps to various associated things, here type is
almost
exactly the same as is used for rails sti/polymorphic associations.
details
is the foreign key pointing to that type.
class WebContentAssociation
# web_contentid | type | details
end
also there are various models, of course, which can be related to a
peice of
web content.
class Country
# countrycode | …
end
class School
# schoolcode | …
end
so a sample WebContentAssociation row might be
42 | ‘country’ | ‘usa’
aka web content # 42 is associated with country ‘usa’
the issue i’m having is this: it seems like a good case for polymorphic
associations and, in the case of belongs to associations this is true,
but for
has_many associations i can’t quite figure out if i’m missing
something, or if
rails is missing something to make the ‘right thing’ happen with these
relationships. so for example, i’d like to be able to say
web_content.countries
but the issue, i think, is not being able to specify the type/
foreign_key
columns for has_many associations in the same way that you can for
polymorphic
belongs to associations.
so while i can do something like this
class WebContent
has_many :web_content_associations, :foreign_key => “web_contentid”
has_many :countries, :through => :web_content_associations
end
class WebContentAssociation
belongs_to :web_content, :foreign_key => “web_contentid”
belongs_to :country, :foreign_key => “details”, :conditions =>
“type=‘country’”
end
class Country
has_many :web_content_associations, :foreign_key =>
“details”, :conditions => “type=‘country’”, :dependent => :destroy
has_many :web_contents, :through => :web_content_associations
end
p web_content.countries
i cannnot do something like
class WebContent
has_many :web_content_associations, :foreign_key => “web_contentid”
has_many :associations, :through => :web_content_associations
end
class WebContentAssociation
belongs_to :web_content, :foreign_key => “web_contentid”
belongs_to :association, :polymorphic => true, :foreign_type =>
“type”, :foreign_key => “details”
end
class Country
has_many :web_content_associations, :as => :association ###
of course this breaks down…
has_many :web_contents, :through => :web_content_associations
end
p web_content.countries
as far as i can tell this is because
has_many :web_content_associations, :as => :associations
pins the sql to
‘where association_id=xx and association_type=yy’
instead of the
‘where details=xx and type=yy’
which is what i need.
in otherwords i need to configure
has_many :foos, :as => :bars
to not use
‘bars_type’ and ‘bars_id’
but two other fields.
anyone know if this is possible?
cheers.
note : the application is using the composite primary key plugin, so
Model.find(id) is a bit perverted from the ‘normal’ ar way…
a @ http://codeforpeople.com/
we can deny everything, except that we have the possibility of being
better. simply reflect on that.
h.h. the 14th dalai lama