I have been advised not to store arrays in my DB, but instead just IDs. In my project, I am storing IDs for line-items. If I don't have a line_item OBJECT, but only IDs, could I still iterate through a loop to get all of the data associated with it?
To explain further...
Traditionally I feel like I have
#line_item
>> <LineItem id: 63, product_id: 2, created_at: time, (etc) >
Then I could do something like
#line_item.title
>> "T-Shirt:Small"
But what if I did
#line_item
and got
>>[12, 14]
Could I do a #line.item.each and get to all the information I need from the just the IDs in the view?? or would I have to create my own scary method?
Hopefully I've posed my question understandably.
Thanks.
You can do this:
#items = [12,14] # your list of ids you got from somewhere
#items.each do |id|
#line_item = LineItem.find(id) # Get the instance for that id.
# do stuff.
end
You could also do something like this:
#line_items = LineItem.find(#id_list)
If the reason you are storing lists of ids is to capture relationships then you should look at the belongs_to and has_many relationships that rails provides. De-normalising data by storing lists is nasty because you don't know how long your list will be. It stops your database from indexing things properly and it's hard to maintain.
I suggest you to use:
LineItem.where(id: [12,14])
As it will return always an array of items. If you try to find for an item who's not in the database you will find a record not found error. This will render an empty array in case no record is found.
As long as you have an array, empty or not, you won't have to rescue the .each method because it won't fail in any case.
Related
I'm grabbing a list of users and storing in #users.
Now I need to find properties related to only this list of users I have queried.
if params[:company].present?
#users = User.where(parent_id: params[:company]).or(User.where(id: params[:company]))
##properties = #properties.where(user_id: params[:company])
end
I would basically like to include #users inside #properties.where()
I need to get each property that has a user_id present in my #users array
edit:
I just did the following which gives me the result, however, I'm sure there's a much better way of doing this via activerecord:
ids = []
#users.each do |user|
ids.push(user.id)
end
#properties = #properties.where(user_id: ids)
#properties.where(user_id: #users.ids)
That should work. It'll take the id of user ids and perform a filter using the IN clause.
Perhaps adding your models and their relationships we can think about something better.
I need to get the previous and next active record objects with Rails. I did it, but don't know if it's the right way to do that.
What I've got:
Controller:
#product = Product.friendly.find(params[:id])
order_list = Product.select(:id).all.map(&:id)
current_position = order_list.index(#product.id)
#previous_product = #collection.products.find(order_list[current_position - 1]) if order_list[current_position - 1]
#next_product = #collection.products.find(order_list[current_position + 1]) if order_list[current_position + 1]
#previous_product ||= Product.last
#next_product ||= Product.first
product_model.rb
default_scope -> {order(:product_sub_group_id => :asc, :id => :asc)}
So, the problem here is that I need to go to my database and get all this ids to know who is the previous and the next.
Tried to use the gem order_query, but it did not work for me and I noted that it goes to the database and fetch all the records in that order, so, that's why I did the same but getting only the ids.
All the solutions that I found was with simple order querys. Order by id or something like a priority field.
Write these methods in your Product model:
class Product
def next
self.class.where("id > ?", id).first
end
def previous
self.class.where("id < ?", id).last
end
end
Now you can do in your controller:
#product = Product.friendly.find(params[:id])
#previous_product = #product.next
#next_product = #product.previous
Please try it, but its not tested.
Thanks
I think it would be faster to do it with only two SQL requests, that only select two rows (and not the entire table). Considering that your default order is sorted by id (otherwise, force the sorting by id) :
#previous_product = Product.where('id < ?', params[:id]).last
#next_product = Product.where('id > ?', params[:id]).first
If the product is the last, then #next_product will be nil, and if it is the first, then, #previous_product will be nil.
There's no easy out-of-the-box solution.
A little dirty, but working way is carefully sorting out what conditions are there for finding next and previous items. With id it's quite easy, since all ids are different, and Rails Guy's answer describes just that: in next for a known id pick a first entry with a larger id (if results are ordered by id, as per defaults). More than that - his answer hints to place next and previous into the model class. Do so.
If there are multiple order criteria, things get complicated. Say, we have a set of rows sorted by group parameter first (which can possibly have equal values on different rows) and then by id (which id different everywhere, guaranteed). Results are ordered by group and then by id (both ascending), so we can possibly encounter two situations of getting the next element, it's the first from the list that has elements, that (so many that):
have the same group and a larger id
have a larger group
Same with previous element: you need the last one from the list
have the same group and a smaller id
have a smaller group
Those fetch all next and previous entries respectively. If you need only one, use Rails' first and last (as suggested by Rails Guy) or limit(1) (and be wary of the asc/desc ordering).
This is what order_query does. Please try the latest version, I can help if it doesn't work for you:
class Product < ActiveRecord::Base
order_query :my_order,
[:product_sub_group_id, :asc],
[:id, :asc]
default_scope -> { my_order }
end
#product.my_order(#collection.products).next
#collection.products.my_order_at(#product).next
This runs one query loading only the next record. Read more on Github.
I have an array #products. Each element of the array is a hash, containing a few fields (but not all) from Product table and the corresponding values.
I have a scope descend_by_popularity in Product which allows me to sort the products based on popularity field. I'd like to sort the array #products using this scope.
What I tried:
#product_group = Array.new
#products.each do |product|
#product_group.push(Product.find(product['id']))
end
#product_group1 = #product_group.descend_by_popularity
But this gives me error:
undefined method `descend_by_popularity' for #<Array:0xb2497200>
I also want to change the sorted Product list back to the format of #products array.
Thanks
Scopes only make sense within the ActiveRecord context for requests to the database (since it is used to change the SQL query). What you did is throwing a lot of products into an array. This array then knows nothing about the scope anymore. You would have to use the scope when you create the #products object. (and it does not seem to make a lot of sense to move the result of a query into an array)
So something like
#products = Product.descend_by_popularity.where(some more stuff)
should work for you. After that you should have the records in the order defined by the scope and can then either use them directly or still push them into an array if that's what you want to do.
With the updated info from the comments it looks like maybe the best way to go would be to first collect only the Product ids from the solr response into an array and then run that as search together with your scope:
#product_group = #products.map{|product| product.id}
#result = Product.where(id: #product_group).descend_by_popularity
this should technically work, peformance is a different question. I would consider aggregating this data into the Solr document, if it doesn't change too often.
Now assuming you are only interested in the order of products as such, you could do something like this to get #products into this order:
#result.map{|r| #products.find{|p| p[:id] == r.id}
though this may slow down things a bit.
Try this: find_by_id as params
#product_group = Array.new
#products.each do |product|
#product_group.push(Product.find(params['id']))
end
and return the array of #product_group
#product_group1 = #product_group.descend_by_popularity
I have been scratching my head over this one for a little while, and though I'm sure its a stupid mistake, I've reached the point where I must consult SO if I am to preserve the hair follicles I have left.
I've written a function in Rails (3.1.2) which should return an array populated with ActiveRecord model objects (users, in this case) which meet a certain criterion. The criterion is that the user's current list (denoted by the field active_list_id) must not be nil. The code follows:
def build_list_array
#lists = Array.new
User.all.each do |user|
#active_list_id = user.active_list_id
#lists<< List.find(#active_list_id) if #active_list_id != nil #TODO WHAT?!? WHY IS THIS RETURNING USERS?
end
end
As you can see, I'm initializing an empty array, cycling through all users and adding their active list to the array if the relevant reference on the user record is not nil. The problem is, this is returning user objects, not list objects.
Here are the associations from the user and list models:
user model:
has_many :lists
has_many :tasks
list model:
belongs_to :user
A brief word about the reference to active_list: A user can have many lists, but only one is active at any time. Therefore, I need to reference that list on the user record. The active list is not a foreign key in the typical sense, then.
I appreciate any help you can give me...Thanks =)
As it stands, your build_list_array will return an array of User because of the behavior of each. When iterating over a collection using each, the call to each returns the original collection.
For example,
list = []
# returns => []
[1,2,3,4,5].each { |number| list << number * 10 }
# returns => [1, 2, 3, 4, 5]
list
# returns => [10, 20, 30, 40, 50]
In your code, the last statement in your build_list_array method is the each call, meaning the return value of each is what is returned by the method. If you simply added a return statement at the end of the method you would be good to go.
def build_list_array
#lists = Array.new
User.all.each do |user|
#active_list_id = user.active_list_id
#lists<< List.find(#active_list_id) if #active_list_id
end
return #lists # Actually return #lists
end
That being said, you should probably use something like Bradley's answer as a basis for more "correct" Rails code.
each always returns the collection it iterates on (no matter what happens inside the block). Sounds like you want to return #lists at the end of your method.
You seem to be making a curious use of instance variables. You could also fetch this in one query via a join, something along the lines of
List.joins('inner join users on active_list_id =lists.id')
Activerecord's Arel is your friend here:
User.where(:active_list_id.not_eq => nil)
Extending Steven's answer, to get the Lists
class User
belongs_to :active_list, :class_name => "List"
def build_list_array
#lists = User.where('active_list_id is not null').map(&:active_list).compact
I'll explain this as best as possible. I have a query on user posts:
#selected_posts = Posts.where(:category => "Baseball")
I would like to write the following statement. Here it is in pseudo terms:
User.where(user has a post in #selected_posts)
Keep in mind that I have a many to many relationship setup so post.user is usable.
Any ideas?
/EDIT
#posts_matches = User.includes(#selected_posts).map{ |user|
[user.company_name, user.posts.count, user.username]
}.sort
Basically, I need the above to work so that it uses the users that HAVE posts in selected_posts and not EVERY user we have in our database.
Try this:
user.posts.where("posts.category = ?", "Baseball")
Edit 1:
user.posts.where("posts.id IN (?)", #selected_posts)
Edit 2:
User.select("users.company_name, count(posts.id) userpost_count, user.username").
joins(:posts).
where("posts.id IN (?)", #selected_posts).
order("users.company_name, userpost_count, user.username")
Just use the following:
User.find(#selected_posts.map(&:user_id).uniq)
This takes the user ids from all the selected posts, turns them into an array, and removes any duplicates. Passing an array to user will just find all the users with matching ids. Problem solved.
To combine this with what you showed in your question, you could write:
#posts_matches = User.find(#selected_posts.map(&:user_id).uniq).map{ |user|
[user.company_name, user.posts.size, user.username]
}
Use size to count a relation instead of count because Rails caches the size method and automatically won't look it up more than once. This is better for performance.
Not sure what you were trying to accomplish with Array#sort at the end of your query, but you could always do something like:
#users_with_posts_in_selected = User.find(#selected_posts.map(&:user_id).uniq).order('username DESC')
I don't understand your question but you can pass an array to the where method like this:
where(:id => #selected_posts.map(&:id))
and it will create a SQL query like WHERE id IN (1,2,3,4)
By virtue of your associations your selected posts already have the users:
#selected_posts = Posts.where("posts.category =?", "Baseball")
#users = #selected_posts.collect(&:user);
You'll probably want to remove duplicate users from #users.