I'm trying to list all the user's products with a probable association where a flag 'notification' is set to zero.
user.probable_associations.where(:notified => 0).collect{|a| Product.where(:id => a.product_id).collect{|p| p.name}}.to_sentence
It seems like using a where and collect method twice within the statement isn't very good. Is there a better way to go about this?
Also, the result is something like
"[\"Product A\"] and [\"Product B\"]"
which is pretty ugly...and I still need to remove the extra punctuation "[\" \"]
instead of something clean like
"Product A and Product B"
EDIT based on Rich's Answer, still have issues because notified is a field in associations NOT product:
has_many :probable_associations, -> { where "associations.category = 3"}, class_name: 'Association', before_add: :set_probable_category
has_many :probable_products, class_name: 'Product', through: :probable_associations, source: :product do
def not_notified
select(:name).where(notified: 0)
end
end
I'd use an ActiveRecord Association extension:
#app/models/user.rb
Class User < ActiveRecord::Base
has_many :products do
def not_notified
select(:name).where(notified: 0)
end
end
end
#-> #user.products.not_notified
That's my contribution, but you could then use #spickermann & #tompave's controbutions and use .flatten.to_sentence
Without knowing what probable_associations does would I rewrite the code to something like this:
product_ids = user.probable_associations.where(:notified => 0).map(&:product_id)
Product.where(:id => product_ids).map(&:name).to_sentence
Assuming that probable_associations is just an ActiveRecord has_many association, and that you want to end up with a list of titles for Product records, you can use this:
ids = user.probable_associations
.where(notified: 0)
.pluck(:product_id)
result = Product.where(id: ids).pluck(:name).to_sentence
It's similar to #spikermann's answer, but pluck(:column_name) is faster than using a block and only extracts the required column from the DB.
Also, the reason your code produces that string is that, by the time you call to_sentence, you have an Array of sub-arrays. Each sub-array contains a single element: a product name.
That's because the second collect is sent to an ActiveRecord::Relation containing just one record.
You could have solved that problem with flatten, but the whole operation could just be refactored.
Related
I have what i feel could be a simple question, and i have this working, but my solution doesn't feel like the "Rails" way of doing this. I'm hoping for some insight on if there is a more acceptable way to achieve these results, rather than the way i would currently approach this, which feels kind of ugly.
So, lets say i have a simple has_many :through setup.
# Catalog.rb
class Catalog < ActiveRecord::Base
has_many :catalog_products
has_many :products, through: :catalog_products
end
# Products.rb
class Product < ActiveRecord::Base
has_many :catalog_products
has_many :catalogs, through: :catalog_products
end
# CatalogProduct.rb
class CatalogProduct < ActiveRecord::Base
belongs_to :catalog
belongs_to :product
end
The data of Catalog and the data of Product should be considered independent of each other except for the fact that they are being associated to each other.
Now, let's say that for Catalog, i have a form with a list of all Products, in say a multi-check form on the front end, and i need to be able to check/uncheck which products are associated with a particular catalog. On the form field end, i would return a param that is an array of all of the checked products.
The question is: what is the most accepted way to now create/delete the catalog_product records so that unchecked products get deleted, newly checked products get created, and unchanged products get left alone?
My current solution would be something like this:
#Catalog.rb
...
def update_linked_products(updated_product_ids)
current_product_ids = catalog_products.collect{|p| p.product_id}
removed_products = (current_product_ids - updated_product_ids)
added_products = (updated_product_ids - current_product_ids)
catalog_products.where(catalog_id: self.id, product_id: removed_products).destroy_all
added_products.each do |prod|
catalog_products.create(product_id: prod)
end
end
...
This, of course, does a comparison between the current associations, figures out which records need to be deleted, and which need to be created, and then performs the deletions and creations.
It works fine, but if i need to do something similar for a different set of models/associations, i feel like this gets even uglier and less DRY every time it's implemented.
Now, i hope this is not the best way to do this (ignoring the quality of the code in my example, but simply what it is trying to achieve), and i feel that there must be a better "Rails" way of achieving this same result.
Take a look at this https://guides.rubyonrails.org/association_basics.html#methods-added-by-has-many-collection-objects
You don't have to remove and create manually each object.
If you have already the product_ids array, I think this should work:
#Catalog.rb
...
def update_linked_products(updated_product_ids)
selected_products = Product.where(id: updated_product_ids)
products = selected_products
end
...
First,
has_many :products, through: :catalog_products
generate some methods for you like product_ids, check this under auto-generated methods to know more about the other generated methods.
so we don't need this line:
current_product_ids = catalog_products.collect{|p| p.product_id}
# exist in both arrays are going to be removed
will_be_removed_ids = updated_product_ids & product_ids
# what's in updated an not in original, will be appended
will_be_added_ids = updated_product_ids - product_ids
Then, using <<, and destroy methods which are also generated from the association (it gives you the ability to deal with Relations as if they are arrays), we are going to destroy the will_be_removed_ids, and append the will_be_added_ids, and the unchanged will not be affected.
Final version:
def update_linked_products(updated_product_ids)
products.destroy(updated_product_ids & product_ids)
products << updated_product_ids - product_ids
end
Hi I want to achieve something like this :
feeds = []
following_companies.each do |follow|
feeds = feeds + Activities.where(:company_id => follow.company_id).order("created_at DESC").limit(5)
end
feeds = feeds.order("created_at DESC")
By the point I use feeds = feeds.order("created_at DESC"), feeds its an Array and throws an exception saying undefined method order for #<Array:0x007f78032e2458>. As long as I know the where clause returns a hash ( or an ActiveRecord list, please correct me if I am wrong). I think the problem is the way I am initializing feeds. Any advise?
When you throw the limit on the end of the where clause, it returns an array instead of Arel. You could sort the array instead of using the arel method order.
feeds = feeds.sort{|f| f.created_at }
Update
If the following companies is still a query you can do
company_ids = following_companies.pluck(:company_id)
If it is an array, you can do this to get all the company_ids
company_ids = following_companies.map {|u| u.location_id }
You can do one query, instead of looping through, for all the feeds which will be
Activities.where(company_id: company_ids).order("created_at DESC")
I'm not sure how you would limit it to 5 for each id though.
feeds.sort_by(&:created_at).reverse will do this directly on feeds after you're done building it with your loop, but you need to do this more efficiently in the first place.
What you're doing above is going to generate a ton of queries if you have any considerable number of followed companies. I'm not sure what your models looks like, but what I can glean from above is something like this:
class User < ActiveRecord::Base
has_many :companies
end
class Company < ActiveRecord::Base
has_many :activities
end
class Activity < ActiveRecord::Base
belongs_to :company
end
You should be able to add a relationship on User to allow you to query all activities at once. Your user model would like something like this:
class User < ActiveRecord::Base
has_many :companies
has_many :activities, through: :companies
end
Then you'd be able to gather your activities by doing user.activities, which would use a join to capture all of the activities, only generating one query. Obviously, your data model may not look exactly like this, but this is the general gist of it.
There's a way to condition something to an associative table of ActiveRecord?
I retrieve segments this way:
#segments = Segment.all
But, a Segment has_many products. See:
models/product.rb:
class Product < ActiveRecord::Base
belongs_to :segment, dependent: :destroy
end
models/segment.rb:
class Segment < ActiveRecord::Base
has_many :products
end
The problem is: I just want to retrieve products whose its status is equals to 1. I can condition something like this using where on Segment model, but how can I achieve this for products?
What I already tried
I found a solution. Take a look:
#segments = Segment.find(:all, include: :products, conditions: {products: {status: 1}})
It worked, but I think the code can be better.
Why I think the code can be better
Well, why should I use include: :products if the association is already live within the models? We're associating things through the model and I'm sure that is something near to enough.
Ideas?
Segment.joins(:products).where("products.status = 1")
You can also use includes instead of joins. But rails will convert it into a join internally since you are using the products table attribute in the query
A few tips, that might help you.
For easy naming purposes, I am considering the status==1 as being active. Of course I have no idea what it means in your specific case.
class Product
ACTIVE=1
def self.active
where(status: ACTIVE)
end
end
Now you write something like:
segment.products.active
and this will return only the active products for the given segment.
The solution you found, which will retrieve all segments with (active) products, could be written differently as follows:
Segment.includes(:products).where(products: {status: 1})
Now, why so elaborate: this actually translates to a sql query, so you have to be a little more explicit about it.
If you only ever want those with a status of 1
class Segment < ActiveRecord::Base
has_many :products, :conditions => { :status => 1 }
end
In rails 3 or
class Segment < ActiveRecord::Base
has_many :products, -> { where status: 1 }
end
In rails 4
Obviously can use status: true if it's a boolean
Then
#segments = Segment.includes(:products)
The association has_many :products makes it possible to use include: :products in your scope. Therefore you shouldn't doubt in your solution. It is right, and it is just the same as solutions presented in the other answers but by other syntacsis.
This should do the job - and it's compatibile with AREL syntax:
#segments = Segment.joins(:products).where(products: {status: 1})
It's quite different that solution with include (or includes, as it would be Rails 3/4), because it generates query with INNER JOIN, while includes generates LEFT OUTER JOIN. Also, includes is usually used for eager loading associated records, not for queries with JOIN.
I have 3 models with "1 to n" associations, like this
Client --1 to n--> Category --1 to n--> Item
In one page, I need to display a list of Items along with their Categories. This page is subject to 3 level of filtering:
Client filtering: I know the client id (I'll use 'id=2' in this example)
Category name: dynamic filter set by the user
Item name: dynamic filter set by the user
And I'm getting more and more confused with ActiveRecord Associations stuff
In my ItemsController#index, I tried this:
categories = Client.find(2).categories
.where('name LIKE ?', "%#{params[:filter_categories]}%")
#items = categories.items
.where('name LIKE ?', "%#{params[:filter_items]}%")
The second line raises a NoMethodError undefined method 'items' for ActiveRecord::Relation. I understand that the first line returns a Relation object, but I cannot find a way to continue from here and get the list of Items linked to this list of Categories.
I also started to extract the list of categories ids returned by the first line, in order to use them in the where clause of the second line, but while writing the code I found it inelegant and thought there may be a better way to do it. Any help would be very appreciated. Thanks
models/client.rb
class Client < ActiveRecord::Base
has_many :categories
has_many :items, through: :categories
...
end
models/category.rb
class Category < ActiveRecord::Base
belongs_to :client
has_many :items
...
end
model/item.rb
class Item < ActiveRecord::Base
belongs_to :category
has_one :client, through: :category
...
end
You can only call .items on a category object, not on a collection. This would work:
#items = categories.first.items
.where('name LIKE ?', "%#{params[:filter_items]}%")
To get what you want, you can do the following:
#items = Item
.where('category_id IN (?) AND name LIKE ?', categories, "%#{params[:filter_items]}%")
Assuming that in the end you are only interested in what is in #items, it would be even better to do it in one query instead of two, using joins:
#items = Item.joins(:category)
.where('items.name LIKE ? AND categories.name = ? AND categories.client_id = 2', "%#{params[:filter_items]}%", "%#{params[:filter_categories]}%")
You can try smth like this:
item_ids = Client.find(2).categories.inject([]) { |ids, cat| ids |= cat.item_ids; ids }
items = Item.find(item_ids)
This how you can get a list of nested objects that associated through another table.
I'm wondering what the easiest/most elegant way of selecting attributes from join models in has_many :through associations is.
Lets say we have Items, Catalogs, and CatalogItems with the following Item class:
class Item < ActiveRecord::Base
has_many :catalog_items
has_many :catalogs, :through => :catalog_items
end
Additionally, lets say that CatalogueItems has a position attribute and that there is only one CatalogueItem between any catalog and any item.
The most obvious but slightly frustrating way to retrieve the position attribute is:
#item = Item.find(4)
#catalog = #item.catalogs.first
#cat_item = #item.catalog_items.first(:conditions => {:catalog_id => #catalog.id})
position = #cat_item.position
This is annoying because it seems that we should be able to do #item.catalogs.first.position since we have completely specified which position we want: the one that corresponds to the first of #item's catalogs.
The only way I've found to get this is:
class Item < ActiveRecord::Base
has_many :catalog_items
has_many :catalogs, :through => :catalog_items, :select => "catalogue_items.position, catalogs.*"
end
Now I can do Item.catalogs.first.position. However, this seems like a bit of a hack - I'm adding an extra attribute onto a Catalog instance. It also opens up the possibility of trying to use a view in two different situations where I populate #catalogs with a Catalog.find or with a #item.catalogs. In one case, the position will be there, and in the other, it won't.
Does anyone have a good solution to this?
Thanks.
You can do something like this:
# which is basically same as your "frustrating way" of doing it
#item.catalog_items.find_by_catalogue_id(#item.catalogs.first.id).position
Or you can wrap it into in an instance method of the Item model:
def position_in_first_catalogue
self.catalog_items.find_by_catalogue_id(self.catalogs.first.id).position
end
and then just call it like this:
#item.position_in_first_catalogue
Just adding answer so that it might help others
CatalogItem.joins(:item, :catalog).
where(items: { id: 4 }).pluck(:position).first
You should be able to do #catalog.catalog_item.position if you provide the other end of the association.
class Catalog < ActiveRecord::Base
belongs_to :catalog_item
end
Now you can do Catalog.first.catalog_item.position.
Why don't You just
#item = Item.find(4)
position = #item.catalog_items.first.position
why do you go through catalogs? It doesn't make any sense to me since you are looking for first ANY catalog!?