Hi Peter,
One way, via two queries would be something like:
# in app/models/user.rb:
def not_yet_listened_recordings
ls = Listening.find_by_sql(["select distinct recording_id from
listenings where user_id=?, self.id])
return Recording.find(:all) if not ls or ls.empty?
criteria_a = []
vals_a = []
ls.each do |l|
criteria_a << "id<>?"
vals_a << l.recording_id.to_i
end
qstr = "select * from recordings where #{criteria_a.join(' and
')}"
sql_a = [qstr] + vals_a
return Recording.find_by_sql(sql_a)
end
...
which you would then be able to call like:
...
user.not_yet_listened_recordings
...
Jeff
On Feb 16, 7:10 am, Peter Browne <[email protected]> wrote:
> I have 3 models with a has_many through association:
>
> class Recording
> has_many :listenings
> has_many :listeners, :through => :listenings, :source => :user
> ...
> end
>
> class User
> has_many :listenings, :foreign_key => "listener_id"
> has_many :listened_recordings, :foreign_key =>
> "listener_id", :through => :listenings, :source => :recording
> ...
> end
>
> class Listening
> belongs_to :recording
> belongs_to :listener, :class_name => "User"
> ...
> end
>
> So I can get the recordings the user has listened to, easily with:
>
> user.listened_recordings
>
> How do create a find method that retrieves all of the recordings the
> user has not listened to?
> The way I have been doing it is:
>
> Recording.all.reject { |r| listened_recordings.include?(r) }
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