I have relations as follows :
Customer has many Orders
Order has many Parts
What I'm trying to do is to assign orders/parts to another customer, but I want to keep the original customer/orders/parts relation. So I tried this (assuming customer is a Customer instance)
another_customer_id = 22
customer.orders.each do |order|
ord = order.dup
ord.customer_id = another_customer_id
ord.save!
order.parts.each do |part|
prt = part.dup
prt.order_id = ord.id
prt.save!
end
end
So I'm assuming once I do customer_two.orders I will get everything as in first customer, but strangely I don't. It seems the first customer has double the orders/parts.
How can I do this in a better way?
update
When I use .dup method the original customers orders are doubled in the database.
When I use .clone instead of .dup nothing happens, another customer still doesn't have orders from original customer
The code you have here looks reasonable to me if you are using Rails >= 3.1. Before Rails 3.1 you need to use clone instead of dup. However, here is another method that you can try:
another_customer_id = 22
customer.orders.each do |order|
ord = Order.create(order.attributes.merge(:customer_id => another_customer_id))
order.parts.each do |part|
Part.create(part.attributes.merge(:order_id => ord.id))
end
end
Related
I have 2 Models: Document and Keywords. They are habtm in relation to each other and they both accepts_nested_attributes_for each other so I can create a nested form. That works well.
So in params, I have
"document"=>{"book_id"=>"1", "keywords"=>{"keywords"=>"term, administration, witness "}, ...
In the controller I put the keywords in a separate array like this :
q = params[:document][:keywords].fetch(:keywords).split(",")
This works well too.
What I now need to do, is get the keywords ids and put them in an array. Each element of that array will populate the join table.
I've tried this :
a = Array.new
q.each do |var|
id = Keyword.select(:id).find_by keyword: var
a << id
id
end
But, this only answers [#<Keyword id: 496>, nil, nil], although the server log shows that all 3 SQL requests are executed and they are correct.
I have also tried this :
a = Array.new
q.map do |e|
Keyword.where(motcle: e).select(:id).find_each do |wrd|
a << wrd.id
end
end
Then again, this only return the FIRST id of the keyword, although the server log shows that all 3 SQL requests are executed.
What I'm trying to get is a = [496, 367, 2398]
So I have 2 questions :
1/ Why are the ids not added to the array, despite the server executing all SQL requests ?
2/ How to write in rails a request would be
SELECT "motclefs"."id" FROM "motclefs" WHERE "motclefs"."motcle" in ('déchéances','comtesse') ORDER BY "motclefs"."id";
Thanks !
The returned value is an object of Keyword. You need to get the id attribute of the object. eg:
id = Keyword.where(keyword: var).select(:id).first.id
A better way to get all the ids would be
a = Keyword.where(keyword: ['term', 'administration', 'witness']).pluck(:id)
# I think this might answer your second question.
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 receive a list of UserIds(about 1000 at a time) sorted by 'Income'. I have User records in "my system's database" but the 'Income' column is not there. I want to retrieve the Users from "my system's database"
in the Sorted Order as received in the list. I tried doing the following using Active Record expecting that the records would be retrieved in the same order as in the Sorted List but it does not work.
//PSEUDO CODE
User.all(:conditions => {:id => [SORTED LIST]})
I found an answer to a similar question at the link below, but am not sure how to implement the suggested solution using Active Record.
ORDER BY the IN value list
Is there any other way to do it?
Please guide.
Shardul.
Your linked to answer provides exactly what you need, you just need to code it in Ruby in a flexible manner.
Something like this:
class User
def self.find_as_sorted(ids)
values = []
ids.each_with_index do |id, index|
values << "(#{id}, #{index + 1})"
end
relation = self.joins("JOIN (VALUES #{values.join(",")}) as x (id, ordering) ON #{table_name}.id = x.id")
relation = relation.order('x.ordering')
relation
end
end
In fact you could easily put that in a module and mixin it into any ActiveRecord classes that need it, since it uses table_name and self its not implemented with any specific class names.
MySQL users can do this via the FIELD function but Postgres lacks it. However this questions has work arounds: Simulating MySQL's ORDER BY FIELD() in Postgresql
I have an app where I retrieve a list of users from a specific country.
I did this in the UsersController:
#fromcanada = User.find(:all, :conditions => { :country => 'canada' })
and then turned it into a scope on the User model
scope :canada, where(:country => 'Canada').order('created_at DESC')
but I also want to be able to retrieve a random person or multiple persons from the country. I found this method that's supposed to be an efficient way to retrieve a random user from the database.
module ActiveRecord
class Base
def self.random
if (c = count) != 0
find(:first, :offset =>rand(c))
end
end
end
end
However, I have a few questions about how to add it, and how the syntax works.
Where would I put that code? Direct in the User model?
Syntax: so that I don't use code that I don't understand, can you explain how the syntax is working? I don't get (c = count). What is count counting? What is rand(c) doing? Is it finding the first one starting at the offset? If rand is an expensive method (hence the need to create a different more efficient random method), why use the expensive 'rand' in this new more efficient random method?
How could I add the call to random on my find method in the UsersController? How to add it to the scope in the model?
Building on question 3, is there a way to get two or three random users?
I wouldn't monkey patch that (or anything else!) into ActiveRecord, putting that into your User would make more sense.
The count is counting how many elements there are in your table and storing that number in c. Then rand(c) gives you a random integer in the interval [0,c) (i.e. 0 <= rand(c) < c). The :offset works the way you think it does.
rand isn't terribly expensive but doing order by random() inside the database can be very expensive. The random method that you're looking at is just a convenient way to get a random record/object from the database.
Adding it to your own User would look something like this:
def self.random
n = scoped.count
scoped.offset(rand(n)).first
end
That would allow you to chain random after a bunch of scopes:
u = User.canadians_eh.some_other_scope.random
but the result of random would be a single user so your chaining would stop there.
If you wanted multiple users you'd want to call random multiple times until you got the number of users you wanted. You could try this:
def self.random
n = scoped.count
scoped.offset(rand(n))
end
us = User.canadians_eh.random.limit(3)
to get three random users but the users would be clustered together in whatever order the database ended up with after your other scopes and that's probably not what you're after. If you want three you'd be better off with something like this:
# In User...
def self.random
n = scoped.count
scoped.offset(rand(n)).first
end
# Somewhere else...
scopes = User.canadians_eh.some_other_scope
users = 3.times.each_with_object([]) do |_, users|
users << scopes.random
scopes = scopes.where('id != :latest', :latest => users.last.id)
end
You'd just grab a random user, update your scope chain to exclude them, and repeat until you're done. You would, of course, want to make sure you had three users first.
You might want to move the ordering out of your canada scope: one scope, one task.
That code is injecting a new method into ActiveRecord::Base. I would put it in lib/ext/activerecord/base.rb. But you can put it anywhere you want.
count is a method being called on self. self will be some class inheriting from ActiveRecord::Base, eg. User. User.count returns the number of user records (sql: SELECT count(*) from users;). rand is a ruby stdlib method Kernel#rand. rand(c) returns a random integer in the Range 0...c and c was previously computed by calling #count. rand is not expensive.
You don't call random with find, User#random is a find, it returns one random record from all User records. In your controller you say User.random and it returns a single random record (or nil if there are no user records at all).
modify the AR::Base::random method like so:
module ActiveRecord
class Base
def self.random( how_many = 1 )
if (c = count) != 0
res = (0..how_many).inject([]) do |m,i|
m << find(:first, :offset =>rand(c))
end
how_many == 1 ? res.first : res
end
end
end
end
User.random(3) # => [<User Rand1>,<User Rand2>,<User Rand3>]
How do I select a single random record for each user, but order the Array by the latest record pr. user.
If Foo uploads a new painting, I would like to select a single random record from foo. This way a user that uploads 10 paintings won't monopolize all the space on the front page, but still get a slot on the top of the page.
This is how I did it with Rails 2.x running on MySQL.
#paintings = Painting.all.reverse
first_paintings = []
#paintings.group_by(&:user_id).each do |user_id, paintings|
first_paintings << paintings[rand(paintings.size-1)]
end
#paintings = (first_paintings + (Painting.all - first_paintings).reverse).paginate(:per_page => 9, :page => params[:page])
The example above generates a lot of SQL query's and is properly badly optimized. How would you pull this off with Rails 3.1 running on PostgreSQL? I have 7000 records..
#paintings = Painting.all.reverse = #paintings = Painting.order("id desc")
If you really want to reverse the order of the the paintings result set I would set up a scope then just use that
Something like
class Painting < ActiveRecord::Base
scope :reversed, order("id desc")
end
Then you can use Painting.reversed anywhere you need it
You have definitely set up a belongs_to association in your Painting model, so I would do:
# painting.rb
default_scope order('id DESC')
# paintings_controller.rb
first_paintings = User.includes(:paintings).collect do |user|
user.paintings.sample
end
#paintings = (first_paintings + Painting.where('id NOT IN (?)', first_paintings)).paginate(:per_page => 9, :page => params[:page])
I think this solution results in the fewest SQL queries, and is very readable. Not tested, but I hope you got the idea.
You could use the dynamic finders:
Painting.order("id desc").find_by_user_id!(user.id)
This is assuming your Paintings table contains a user_id column or some other way to associate users to paintings which it appears you have covered since you're calling user_id in your initial code. This isn't random but using find_all_by_user_id would allow you to call .reverse on the array if you still wanted and find a random painting.