I have an Item which I split the table with cache_item. CachItem contains some serialized fragments. Like this:
class Item < ActiveRecord::Base
has_one :cache_item
end
class CacheItem < ActiveRecord::Base
belongs_to :item
end
how would I tell it to create one and save it automatically?
I do something like this:
if !cache_item
CacheItem.create! item_id: id
self.reload # seems like I shouldn't have to do this
end
but seems like there should be a single call. Is there?
For a has_many, I can do:
>item.comments.count
>1
>item.comments.create! # inserts with proper information
>2
What is the pattern for a has_one?
For a has_one association, you can use create_association! as documented: http://guides.rubyonrails.org/association_basics.html#has-one-association-reference
In your case
item.create_cached_item!
For an Item that has_many Comment(s) you use:
Item.comments.create()
And for an Item that has_one Comment you use:
Item.create_comment
Related
I am trying to save an array of multiple ids (item_variation_ids) to a model called items_stock from item variations model. In a column called item_variation_ids in item_stock, it is saving the ids like [1,2,3] for twice. I want the item_variation_ids to be saved once only with 1,2,3 in a single column.
My item_variation model
#app/models/item_variation
class ItemVariation < ApplicationRecord
belongs_to :item
validates_associated :item
after_save :add_to_item_stock
def add_to_item_stock
ItemStock.create(item_variation_ids: ItemVariation.ids, items_id: items_id)
end
end
My item model
#app/models/item
class Item < ApplicationRecord
has_many :item_variations, foreign_key: :items_id
has_many :item_stocks, foreign_key: :items_id
accepts_nested_attributes_for :item_stocks
end
My item_stock model
#app/models/item_stock
class ItemStock < ApplicationRecord
belongs_to :item
end
But how do you know which ItemVariation ids should go on that ItemStock? and you are creating one ItemStock each time any variation gets saved. I don't even think you need to set that ids array since the ItemStock already belongs to an Item which has many variations (#item_stock.item.variations and you are done).
Also now you are talking about a stock_qty attribute you never mentioned before, you are never setting it on the callback and you didn't show your database schema. where does that amout come from? is an attribute on the variation that you want to sum to the current item_stock?
I also don't understand why an item has many item stocks for the code you are showing.
I'll do a wild guess and suggest you do something like:
ItemStock
belongs_to :item
belongs_to :item_variation
end
ItemVariation
after_save :add_to_item_stock
def add_to_item_stock
item_stock = self.item.item_stock.where(item_variation_id: self.id).first_or_initialize
item_stock.stock_qty = self.stock_qty
item_stock.save
end
end
but as I said, it's a wiiiiild guess. I'd recommend you to first try to understand what you are doing, because it seems like you just copied to code from that question you linked and you are no actually understanding it.
There is a cool feature for has_many in Rails. I can write
class Article < AR::Base
has_many :comments
has_one :another_association
and voila! method comment_ids= created, which I can use in strong parameters and mass assignment. Somethind like #article.comment_ids = [1,2,3]
I need something similar for has_one, like #article.another_association_id = 1. But I get NoMethodError exception. Is there any way to make this method works?
Has one has a different syntax.
#article.build_another_association
#article.create_another_association
See the guides for more info
Use attr_accessible
Specifies a white list of model attributes that can be set via mass-assignment
So you can add it like this assuming you created and ran the migration already:
class Article < AR::Base
has_many :comments
has_one :another_association
attr_accessible :another_association_id
But if it's Rails 4 you may need to handle it in the controller.
You have the direction of the association reversed.
With has_one, the other class should have an article_id to refer to a record in your articles table.
If you want articles.another_association_id, then you should specify belongs_to :another_association.
This method should only be used if the other class contains the foreign key. If the current class contains the foreign key, then you should use belongs_to instead.
http://api.rubyonrails.org/classes/ActiveRecord/Associations/ClassMethods.html#method-i-has_one
If you want to simulate the way has_many works you could try this:
class Article < AR::Base
has_one :page
def page_id=(int_id)
self.page = Page.find(int_id)
end
end
#article.page_id = 3
I've got two models with a has_many / has_many relationship. I have a variable exp_ids which is an array of integers representing the id's of some ExperienceLevel records. I need to write a query that will select all JobDescriptions that have an ExperienceLevel with one of those ids.
The query must work on an existing ActiveRelation object called job_descriptions, which is being passed through some flow controls in my controller to filter the results based on my params.
I've tried these queries below and some other variations, but with little success. As far as I can tell, ActiveRecord thinks that experience_levels is an attribute, which is causing it to fail.
job_descriptions.where(experience_levels: exp_ids)
job_descriptions.joins(:experience_levels).where(experience_levels.id: exp_ids)
job_descriptions.joins(:experience_levels).where(experience_levels: exp_ids)
job_descriptions.joins(:experience_levels).where("experience_levels.id IN exp_ids")
job_descriptions.includes(:experience_levels).where("experience_levels.id = ?", exp_ids).references(:experience_levels)
Here are my models:
class JobDescription < ActiveRecord::Base
has_many :job_description_experience_levels
has_many :experience_levels, through: :job_description_experience_levels
end
class JobDescriptionExperienceLevel < ActiveRecord::Base
belongs_to :job_description
belongs_to :experience_level
end
class ExperienceLevel < ActiveRecord::Base
has_many :job_description_experience_levels
has_many :job_descriptions, through: :job_description_experience_levels
end
I'm not sure if what I want to do is even possible. I've used a similar approach for another job_description filter where I selected the company_id, but in the case, company_id was an attribute of JobDescription.
Try this:
job_descriptions.joins(:job_description_experience_levels).where(job_description_experience_levels: { experience_level_id: exp_ids })
job_descriptions.joins(:experience_levels).where(experience_levels: {id: exp_ids})
Try this one. Note the lack of plural on the experience level.id
job_descriptions.includes(:experience_levels).where("experience_level.id = ?", exp_ids).references(:experience_levels)
product.rb
has_many :votes
vote.rb
belongs_to :product
Every time, i use sorting in my index controller:
index_controller.rb
def index
#products = Product.all.sort { |m| m.votes.count }
end
So, i think it would be good to cache votes count for each product (create additional column votesCount in products table)?
If yes, can i preform that using before_save and before_delete callbacks in vote.rb model?
Or what is the best practice method?
Give me some examples please.
I guess you are looking for counter_cache
The :counter_cache option can be used to make finding the number of belonging objects more efficient
Consider these models:
class Order < ActiveRecord::Base
belongs_to :customer, counter_cache: true
end
class Customer < ActiveRecord::Base
has_many :orders
end
With this declaration, Rails will keep the cache value up to date, and then return that value in response to the size method.
Although the :counter_cache option is specified on the model that includes the belongs_to declaration, the actual column must be added to the associated model. In the case above, you would need to add a column named orders_count to the Customer model
I have a simple Customer model with a has many relationship with a Purchase model.
class Customer < ActiveRecord::Base
has_many :purchases
end
I am repeatedly finding that I need to order Customer.purchases in my views in the following way:
#customer.purchases.joins(:shop).order("shops.position").order(:position) #yes, two orders chained
In the interest of keeping things DRY, I'd like to put this somewhere centralized so I don't have to repeatedly do it. Ideally, I'd like to make it the default ordering for Customer.purchases. For example:
class Customer < ActiveRecord::Base
has_many :purchases, :order => joins(:shop).order("shops.position").order(:position)
end
Obviously the above doesn't work. How should I do this?
In your customer model you specified joins(:shop) is the value for the key :order. I think here is the problem, So you can use the joins as a key instead of order like below,
class Customer < ActiveRecord::Base
has_many :purchases, :joins => [:shop], :order => "shops.position"
end
I think it may work.
In your purchases model, you can create a class method:
Purchase.rb:
def self.order_by_position
joins(:shop).order("shops.position").order(:position)
end
Then you can say things like:
#customer.purchases.order_by_position
Purchase.order_by_position
You could create a method on Customer that returns ordered purchases:
class Customer < ActiveRecord::Base
has_many :purchases
def ordered_purchases
purchases.joins(:shop).order("shops.position").order(:position)
end
end
and call #customer.ordered_purchases from your views.