Rails - Show all models that belongs

if have user has_many :problems, assuming have set necessary association between user , problem , how can like:

  # userscontroller.rb   def students_problems      @userid = params[:user_id]      @problems = give me problems associated @userid   end

@user = user.find(params[:user_id])  @problems = @user.problems

ideally want in model if plan more code. can create model method controller.

@problems = user.name_your_method_here(params[:user_id])

then in user model have

self.name_your_method_here(user_id)   user.find(user_id).problems end

and might want add conditionals make sure user_id matches real user i'll leave do.

edit: lebreeze suggests, might wise change name of method different, @ least relates you're doing code.

Brande