I have models set up similar to this:
class Book < ActiveRecord::Base
has_many :histories, as: :object
end
class Magazine < ActiveRecord::Base
has_many :histories, as: :object
end
class Action < ActiveRecord::Base
belongs_to :object, polymorphic: true
default_scope order(:done_at)
# a history contains an action and the time that action
# occurred on the object it belongs to
end
Now, I want to get a list of the 5 lastest actions that have occurred on all objects. So I can do something like:
Action.limit(5)
However, the problem is that if two actions have recently occurred on the same book, both actions will be retrieved. I want to only retrieve the lastest one. How do I achieve this?
Figured out that what I wanted was the group option. So I can do something like:
Action.group(:object_id).group(:object_type).limit(5)
Related
I have a problem or dilemma after implementing polymorphic association following this: All the code is located here,
I have implemented this model:
Let's suppose that I also need the subscription to magazines. It will also be something similar to the other two
class Magazines < ApplicationRecord
has_many :subscriptions, as: :subscribable
end
class User < ApplicationRecord
has_many :subscriptions
has_many :podcasts, through: :subscriptions, source: :subscribable, source_type: 'Podcast'
has_many :newspapers, through: :subscriptions, source: :subscribable, source_type: 'Newspaper'
has_many :magazines, through: :subscriptions, source: :subscribable, source_type: 'Newspaper'
end
class Subscription < ApplicationRecord
belongs_to :subscribable, polymorphic: true
belongs_to :user
end
It works well, the problem now is ok I can handle like three types of subscription
MagazineSubscription, PodcastSubscription and NewspaperSubscription. The three have the same attributes and same behaviour, but belongs to different model. What happens If after doing that I need some kind of MTI or STI with the subscription classes. i.e. the MagazineSubscription have different behaviour and maybe other attributes. There is an easy way on this to accomplish this new requirement like creating a Subscription class that handles all that the polymorphic association and the other models:
class Subscription < ActiveRecord::Base
self.inheritance_column = :sti_subscription
belongs_to :subscribable, polymorphic: true
belongs_to :user
def _type=(sType)
sti_subscrition = sType.to_s.classify.constantize.base_class.to_s + "Subscription"
super(sType.to_s.classify.constantize.base_class.to_s)
end
end
class MagazineSubscription < Subscription
# new behaviour here
end
or I must follow something similar to this with the Subscription class handling two polymorphic relations, with the subscribable and his descendants
So my question is when I have used polymorphic association is an easy way to use that to set STI or MTI, or I need to make a new approach
I have three classes: User, Subscription and Plan. I want to load all of the Plans that the User doesn't have. What's the best way to do it in Rails?
I have two collections: current_user.subscriptions and Plan.where(active: true)
And i am using mongoid
def dashboard
#plans = Plan.where(active: true)#.each { #plans.delete_if has_current_user_plan subscription.title }
end
def has_current_user_plan(name)
current_user.subscriptions.where(title: name, active: true).exists?
end
class User
has_many :subscriptions
class Subscription
belongs_to :plan
belongs_to :user
class Plan
has_many :subscriptions
AR:
class User < ActiveRecord::Base
has_many :subscriptions
has_many :plans, through: :subscriptions # !!!
end
Plan.where(active: true).where.not(id: current_user.plans)
I'm not really sure what's the best approach for Mongoid because I've never used it. From what I've gather from the documentation, something like the following might work although I'm not running the code.
Plan.where(active: true).not_in(_id: Subscription.where(user_id: current_user.id).pluck(:plan_id))
I have two ActiveRecord models:
class Class < ActiveRecord::Base
(...)
has_many :class_to_teacher, dependent: :destroy
end
class Teacher < ActiveRecord::Base
has_many :classes,
through: :class_to_teacher
end
class ClassToTeacher < ActiveRecord::Base
belongs_to :klass
belongs_to :teacher
end
When I remove Class I don't remove it completly only I remove record from ClassToTeacher record. I need to keep this data:
def leave(class, teacher)
teacher.klasses.delete(class)
end
Now I have to get all associated classes (classes which contains record in ClassToTeacher). How to do this the best? Thanks for all answers.
You should try something like that:
Class.includes(:class_to_teacher).where('class_to_teacher.id is not null').references(:class_to_teacher).all
Assuming that you have an 'id' field in your database for the ClassToTeacher
I guess there's a lot of ways to get there but the simplest one is probably this:
Klass.where(id: KlassToTeacher.select(:klass_id))
This will result in a single query with a sub-query. Note that I changed the names of the models because Class is already defined in Ruby and you're just asking for trouble.
Using: Rails 4.1.4, PostgreSQL 9.1.13
Hi. I'm have a simple problem, but for some reason I can't get it done. The picture is this:
Models
class Article < ActiveRecord::Base
belongs_to :user
has_many :votes
end
class User < ActiveRecord::Base
has_many :articles
has_many :votes
end
class Vote < ActiveRecord::Base
belongs_to :article
belongs_to :user, scope: :hotel_id
validates_inclusion_of :value, in: 0..5
validates_uniqueness_of :user_id, :article_id
end
Idea
Each User can Vote for each Article but only once (to avoid multiple voting).
Vote model has a 'value' attribute that is the range 0..10.
ArticlesController except standard CRUD methods has action #showcase which must return 5 articles with the top votes rating from the DB and sort them in the descending order (and render the respective view).
So I understand that the proper way is to write the class method in the Article Model (smth. like "by_top_votes") and use it in the ArticlesController#showcase:
def showcase
#top_five_articles = Article.by_top_votes
end
The problem is that I can't write the proper query to the DB which will: 1)find articles, 2)find all votes of the each article, 3) sum all values of the respective article's votes, 4)sort them (this step I know how to do).
Thank you for reading and for the help.
P.S. Maybe my way to solve problem is almost wrong. If this so, please tell my the right one.
Ok, I've done it by myself. If anybody will stuck with the same problem, here is solution for it.
1. In Vote model summarize the vote's values:
def self.sum_value
sum(:value)
end
2. Add new attribute (and column) to Article - user_rating:integer.
3. In the Article model define two class methods:
# assign user_rating attribute with the sum of all votes values
def set_user_rating
user_rating = self.votes.sum_value
self.update_attribute(:user_rating, user_rating)
end
# get top 5 articles by user_rating value from db
def self.top_by_user_rating
Article.order(:user_rating).reverse_order.limit(5)
end
4. In the ArticlesController define showcase action:
def showcase
#top_articles = Article.top_by_user_rating
end
5. In the VotesController define create action:
def create
#article = Article.find(params[:article_id])
#vote = #article.votes.create(vote_params)
if #vote.save
#article.set_user_rating
redirect_to #article, notice: "Thanks for your vote"
else
.
end
end
It works and tests are passing.
A user can create a post. Posts have comments. A comment must belong to both a user and a post, however not necessarily the user who created the post. Is the following the best way to model this:
class User < ActiveRecord::Base
has_many :posts
has_many :comments
end
class Post < ActiveRecord::Base
belongs_to :user
has_many :comments
end
class Comment < ActiveRecord::Base
belongs_to :user
belongs_to :post
end
If so, what is the best practice for ensuring:
user.comments.new cannot be called. I want all new posts to be created using the post they are associated with.
The id of the user creating the comment is properly set when calling post.comments.new
Otherwise, what is a better way to model this relationship?
Your models are fine.
To set the author of the comment, you'd have to do that in your controller:
#comment = post.comments.new do |c|
c.user = current_user
end
Just don't use user.comments.new. Why do you want to make it impossible to use it?