I have a Sinatra app using the Sequel ORM in which I'm trying to list only Categories that have one or more Posts.
So, if I have two categories in the database; "Apples" and "Oranges", and one Post assigned to "Apples", then when I list the current categories I only want the "Apples" category to be provided.
After much hair-pulling I finally managed to get it working with the following;
class Post < Sequel::Model
many_to_one :category
end
class Category < Sequel::Model
one_to_many :posts
dataset_module do
def with_posts
where(id: Post.select(:category_id))
end
end
end
#categories = Category.with_posts
If there's a better way of doing this in Sequel please do let me know.
Try Jeremy's counter cache https://github.com/jeremyevans/sequel_postgresql_triggers
# In your migration:
pgt_counter_cache :categories, :id, :posts_count, :posts, :category_id
# And in your code:
categories = Category.exclude(posts_count: 0).all
The documentation isn't very good so here are the arguments: https://github.com/jeremyevans/sequel_postgresql_triggers/blob/master/lib/sequel_postgresql_triggers.rb#L27
Related
Sorry to ask this question but I'm really newbie with Ruby and I need help to update several records on my database.
I'm using ActiveRecord to query the database. Let say I have a table Product that contains SubProduct that also contains SubSubProduct. Now I would like to write a simple query to get all SubSubProduct of Product.
To get a list of SubSubProduct I usually do this
ssp = SubSubProduct.where(sub_sub_type: "example")
Now to use a where clause on relational element how can I do
ssp = SubSubProduct.where(sub_sub_type: "example", SubProduct.Product.type: "sample")
Set up ActiveRecord associations in your models:
#app/models/product.rb:
class Product < ActiveRecord::Base
has_many :sub_products
end
#app/models/sub_product.rb:
class SubProduct < ActiveRecord::Base
belongs_to :product
end
#app/models/sub_sub_product.rb:
class SubSubProduct < ActiveRecord::Base
belongs_to :sub_product
end
What you wanted:
ssp = SubSubProduct.where(sub_sub_type: "example", SubProduct.Product.my_type: "sample")
The correct syntax:
ssp = SubSubProduct.includes(sub_product: :product).where(sub_sub_type:"example", products: {my_type: "toto"})
This is performed via associations.
class SubSubProduct
has_many :products
end
Then you can do things like
sub_product.products
and it will product all the products associated with them.
Try a nested includes:
`Product.includes(subproducts: :subsubproducts)'
For this, you'll want to set up ActiveRecord associations in your models:
In product.rb:
class Product < ActiveRecord::Base
has_many :sub_products
has_many :sub_sub_products, through: :sub_products
end
In sub_product.rb:
class SubProduct < ActiveRecord::Base
belongs_to :product
has_many :sub_sub_products
end
In sub_sub_product.rb:
class SubSubProduct < ActiveRecord::Base
belongs_to :sub_product
end
Then, if you have a Product and want its SubSubProducts, you can use:
# p is a Product object
p.sub_sub_products
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.
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)
I've setup a nested form in my rails 3.2.3 app, it's working fine, my models are:
class Recipe < ActiveRecord::Base
attr_accessible :title, :description, :excerpt, :date, :ingredient_lines_attributes
has_and_belongs_to_many :ingredient_lines
accepts_nested_attributes_for :ingredient_lines
end
and:
class IngredientLine < ActiveRecord::Base
attr_accessible :ingredient_id, :measurement_unit_id, :quantity
has_and_belongs_to_many :recipes
belongs_to :measurement_unit
belongs_to :ingredient
end
As above, a Recipe can have multiple IngredientLines and vice versa.
What I'm trying to avoid is record duplication on IngredienLine table.
For example imagine that for recipe_1 an IngredientLine with {"measurement_unit_id" => 1, "ingredient_id" => 1, "quantity" => 3.5} is associated, if for recipe_5 the IngredientLine child form is compiled by the user with the same values, I don't want a new record on IngredientLine table, but only a new association record in the join table ingredient_lines_recipes.
Note that currently I dont't have any IngredientLine controller as saving and updating IngredientLines is handled by nested form routines. Even my Recipe controller is plain and standard:
class RecipesController < ApplicationController
respond_to :html
def new
#recipe = Recipe.new
end
def create
#recipe = Recipe.new(params[:recipe])
flash[:notice] = 'Recipe saved.' if #recipe.save
respond_with(#recipe)
end
def destroy
#recipe = Recipe.find(params[:id])
#recipe.destroy
respond_with(:recipes)
end
def edit
respond_with(#recipe = Recipe.find(params[:id]))
end
def update
#recipe = Recipe.find(params[:id])
flash[:notice] = 'Recipe updated.' if #recipe.update_attributes(params[:recipe])
respond_with(#recipe)
end
end
My guess is that should be enough to override the standard create behavior for IngredientLine with find_or_create, but I don't know how to achieve it.
But there's another important point to take care, imagine the edit of a child form where some IngredientLines are present, if I add another IngredientLine, which is already stored in IngredientLine table, rails of course should not write anything on IngredientLine table, but should also distinguish between child records already associated to the parent, and the new child record for which needs to create the relation, writing a new record on the join table.
Thanks!
in Recipe model redefine method
def ingredient_lines_attributes=(attributes)
self.ingredient_lines << IngredientLine.where(attributes).first_or_initialize
end
Old question but I had the same problem. Forgot to add :id to white list with rails 4 strong_parameters.
For example:
widgets_controller.rb
def widget_params
params.require(:widget).permit(:name, :foos_attributes => [:id, :name, :_destroy],)
end
widget.rb
class Widget < ActiveRecord::Base
has_many :foos, dependent: :destroy
accepts_nested_attributes_for :foos, allow_destroy: true
end
foo.rb
class Foo < ActiveRecord::Base
belongs_to :widget
end
I have run into a similar situation and found inspiration in this answer. In short, I don't worry about the duplication of nested models until save time.
Translated to your example, I added autosave_associated_records_for_ingredient_lines to Recipe. It iterates through ingredient_lines and performs a find_or_create as your intuition said. If ingredient_lines are complex, Yuri's first_or_initialize approach may be cleaner.
I believe this has the behavior you're looking for: nested models are never duplicated, but editing one causes a new record rather than updating a shared one. There is the strong possibility of orphaned ingredient_lines but if that's a serious concern you could choose to update if that model has only one recipe with an id that matches the current one.
I have a "two middleman" model setup as shown below:
User
has_many :comments
has_many :ratings
Comment
belongs_to :user
belongs_to :movie
Rating
belongs_to :user
belongs_to :movie
Movie
has_many :comments
has_many :ratings
Whats the best way to get all Movies that a User is associated with (either commented on or rated)?
I'd like to be able to call User.get_movies(user_id) and get back an ActiveRecord::Relation object so that it's chainable (i.e. User.get_movies(user_id).limit(3).order(...)). This returns a regular old array, and I suspect I'm hitting the database way more than I need to be.
def self.get_movies(user_id)
user = self.where(:id => user_id).includes({:comments => :movie}, {:ratings => :movie})
movies = []
user.comments.each do |comment|
movies.push(comment.movie)
end
user.ratings.each do |rating|
movies.push(rating.movie)
end
movies.uniq!
end
def movies
Movie.includes(:ratings, :comments).where("`ratings`.user_id = ? OR `comments`.user_id = ?", self.id, self.id)
end
Untested, but I'm pretty sure using a joins instead of includes also works.