conditional association

rubyonrails-talk
1

hello ,

i have an association as follows. A user is of type “author” or “reader”. In the user table is a column called user_type_id that references a user_type table of 2 records, author, reader. What i am trying to do is the following:

Create an association such that a user has_one :profile, but the :profile is either author_profile table or reader_profile table (they have too many different attributes to make one profile table) depending on the user type. is there a way to specify a conditional has_one in the user model that would allow access to ‘user.profile’ but know which model to reference ? Either that or do a conditional set_table_name depending on a variable …

Any help here appreciated.

Thanks

Adam

2

hello ,

i have an association as follows. A user is of type "author" or
"reader". In the user table is a column called user_type_id that
references a user_type table of 2 records, author, reader. What i
am trying to do is the following:

Create an association such that a user has_one :profile, but
the :profile is either author_profile table or reader_profile table
(they have too many different attributes to make one profile table)
depending on the user type. is there a way to specify a conditional
has_one in the user model that would allow access to 'user.profile'
but know which model to reference ? Either that or do a conditional
set_table_name depending on a variable ..

Perhaps a polymorphic association ? Or alternatively use STI, and have
a base class User with the common functionality and both Author and
Read inheriting from that. Then it's easy, because you just stick
has_one :author_profile in Author and has_one :reader_profile in Reader.

Fred

3

> i have an association as follows. A user is of type "author" or
> "reader". In the user table is a column called user_type_id that
> references a user_type table of 2 records, author, reader. What i
> am trying to do is the following: > > Create an association such that a user has_one :profile, but
> the :profile is either author_profile table or reader_profile table
> (they have too many different attributes to make one profile table)
> depending on the user type. is there a way to specify a conditional
> has_one in the user model that would allow access to 'user.profile'
> but know which model to reference ? Either that or do a conditional
> set_table_name depending on a variable .. > Perhaps a polymorphic association ? Or alternatively use STI, and have
a base class User with the common functionality and both Author and
Read inheriting from that. Then it's easy, because you just stick
has_one :author_profile in Author and has_one :reader_profile in Reader.

Yep, I was going to suggest STI. This is exactly the sort of situation for which it is appropriate.

Fred > Any help here appreciated. > > Thanks > Adam

--Greg

4

Well, it depends on how much the Author and Reader models have in common, as to whether it makes sense to use STI, i.e. how many attributes they have in common.

If it distorts reality too much to force them to use a single table, then a polymorphic association is probably the better approach.

5

I think the STI for the user model makes the most sense.

class User < Activerecord::Base

class Reader < User

has_one :reader_profile

end

class Author < User

has_one :author_profile

end

end

Assuming I had a common controller called profile and wanted to display the appropriate profile is there an easier way then

def show

case current_user.type

when ‘Reader’

@profile = ReaderProfile.find(:first, :conditions => [“user_id = ?”,current_user.id)

render :template => ‘reader_profile’

when ‘Author’

@profile = AuthorProfile.find(:first, :conditions => [“user_id = ?”,current_user.id)

render :template => ‘author_profile’

end

end

6

You might want to add

attr_accessor :profile

to your User and then have the subclasses populate @profile on the user instance as necessary. Off the top of my head you'd probably end up with something like:

class User < Activerecord::Base   attr_accessor :profile ene

class Reader < User   has_one :reader_profile   def profile     @profile ||= self.reader_profile     @profile   end end

class Author < User   has_one :author_profile   def profile     @profile ||= self.author_profile     @profile   end end

By doing something like that your view could simply work with @user.profile without worrying about how to load the data. As for rendering different templates, you should probably render only one, and let that single template render the common components (User stuff) and then farm out the custom stuff to partials.

HTH, AndyV

7

You can do something like this:

class Reader < User   has_one :profile, :class_name => 'ReaderProfile', :foreign_key => :reader_id end

class Author < User   has_one :profile, :class_name => 'AuthorProfile', :foreign_key => :author_id end

def show   render :template => current_user.profile.class.name.underscore end