Rails where with join, but return object of parent?

Suppose I have a class that represents a list of movies, belonging to a user:

class User < ActiveRecord::Base
    has_one :movie_list
end

class MovieList < ActiveRecord::Base
    belongs_to :user

    has_many :movie_list_movie_relationships
    has_many :movies, :through => :movie_list_movie_relationships
end

class Movie < ActiveRecord::Base
    has_many :movie_list_movie_relationships
    has_many :movie_lists, :through => :movie_list_movie_relationships
end

class MovieListMovieRelationship < ActiveRecord::Base
   开发者_高级运维 belongs_to :movie
    belongs_to :movie_list
end

Is there any way to have a method on MovieList that returns a MovieList containing only movies with, for example, a specific release year. I want something like:

class MovieList < ActiveRecord::Base
    ....
    def for_year year
        movies.where(:year => year)
    end
end

EXCEPT that I want the result to be a MovieList itself, whereas this returns an array of Movies. So I could do, for example:

list = User.first.movie_list.for_year(1999)
list.id # would give the id of the MovieList = User.first.movie_list.id
list.movies.first.id # would give the id of the first movie in list

I have a feeling that I'm either a) faced with this problem because my design is bad, and it would be great if someone could explain how I should design this, or b) asking for something relatively mundane but I just don't know the right terminology.

Thanks!

Edit

I have specific reasons for wanting a MovieList and not an array of Movies. For one, I've written the question with User has_one :movie_list but in reality a User has_many :movie_lists (e.g., "Movies I have on DVD", "Movies I want to see", etc). That's why I don't just use a simple join between User and Movie. I want a MovieList because I want the id of the list to get passed around to make it easy to add a movie to a specific list; I have a MovieListMovieRelationshipController. I think what I'm going to end up having to do is fetch the movies as an array and just pass around the list id manually.

Edit 2

Here's what I ended up doing, as per @normalocity and the ensuing comments. Any further comments/suggestions are appreciated :)

class MovieList
    ...
    def limit_to_year year
        new_list = MovieList.new(self.attributes)
        new_list.id = self.id
        new_list.movies = []

        limited_movies = movies.where(:year => year)
        new_list.movies = limited_movies
        return new_list
    end
end

---

You can't do what you're hoping for directly, no, but it's simple enough to create an empty MovieList, and then add the array of movies from your for_year method to the new MovieList. You can even make the query for the array of associated Movie objects faster/simpler via a named_scope.

• Create a named scope to get all Movies from a specific year:

In Movie class:

named_scope :for_year, lambda { |year| {:conditions => ["year = ?", year]} }

Now, every time you call Movie.for_year("1945") you get back an array of Movie objects from that year.

Then...

• Create a new MovieList (that belongs to NO user), and add the results from #1 to the list

This might work: movies1945 = MovieList.create(:movies => Movie.for_year("1945")

If it doesn't work, you might have to split up the creation of the new MovieList object, and the assignment of values to the Movie collection.

If you need to distinguish between a simple list of Movies (what's the difference between that and an Array, I don't know, but if that distinction is necessary), and the Movies that a particular user has in their collection, then you could separate your classes into MovieList (just a list of movies) and a Collection (the movies that a given user has).

If you don't need that, then the 1945 movie list could either have a nil user, or (say your web site is called imdb.com) you could create a dummy user account called "imdb", and have the list belong to that user.