I am starting to create my sites in Ruby on Rails these days instead of PHP.
I have picked up the language easily but still not 100% confident with associations :)
I have this situation:
User Model
has_and_belongs_to_many :roles
Roles Model
has_and_belongs_to_many :users
Journal Model
has_and_belongs_to_many :roles
So I have a roles_users table and a journals_roles table
I can access the user roles like so:
user = User.find(1)
User.roles
This gives me the roles assigned to the user, I can then access the journal model like so:
journals = user.roles.first.journals
This gets me the journals associated with the user based on the roles. I want to be able to access the journals like so user.journals
In my user model I have tried this:
def journals
self.roles.collect { |role| role.journals }.flatten
end
This gets me the journals in a flatten array but unfortunately I am unable to access anything associated with journals in this case, e.g in the journals model it has:
has_many :items
When I try to access user.journals.items it does not work as it is a flatten array which I am trying to access the has_many association.
Is it possible to get the user.journals another way other than the way I have shown above with the collect method?
Hope you guys understand what I mean, if not let me know and ill try to explain it better.
Cheers
Eef
If you want to have user.journals you should write query by hand. As far as I know Rails does has_many :through associations (habtm is a kind of has_many :through) one level deep. You can use has_many with finder_sql.
user.journals.items in your example doesn't work, becouse journals is an array and it doesn't have items method associated. So, you need to select one journal and then call items:
user.journals.first.items
I would also modify your journals method:
def journals
self.roles(:include => :journals).collect { |role| role.journals }.flatten.uniq
end
uniq removes duplicates and :inlcude => :journals should improve sql queries.
Similar question https://stackoverflow.com/questions/2802539/ruby-on-rails-join-table-associations
You can use Journal.scoped to create scope with conditions you need. As you have many-to-many association for journals-roles, you need to access joining table either with separate query or with inner select:
def journals
Journal.scoped(:conditions => ["journals.id in (Select journal_id from journals_roles where role_id in (?))", role_ids])
end
Then you can use user.journals.all(:include => :items) etc
Related
I have a product model setup like the following:
class Product < ActiveRecord::Base
has_many :product_atts, :dependent => :destroy
has_many :atts, :through => :product_atts
has_many :variants, :class_name => "Product", :foreign_key => "parent_id", :dependent => :destroy
end
And I want to search for products that have associations with multiple attributes.
I thought maybe this would work:
Product.joins(:product_atts).where(parent_id: params[:product_id]).where(product_atts: {att_id: [5,7]})
But this does not seem to do what I am looking for. This does where ID or ID.
So I tried the following:
Product.joins(:product_atts).where(parent_id: 3).where(product_atts: {att_id: 5}).where(product_atts: {att_id: 7})
But this doesn't work either, it returns 0 results.
So my question is how do I look for a model by passing in attributes of multiple join models of the same model type?
SOLUTION:
att_ids = params[:att_ids] #This is an array of attribute ids
product = Product.find(params[:product_id]) #This is the parent product
scope = att_ids.reduce(product.variants) do |relation, att_id|
relation.where('EXISTS (SELECT 1 FROM product_atts WHERE product_id=products.id AND att_id=?)', att_id)
end
product_variant = scope.first
This is a seemingly-simple request made actually pretty tricky by how SQL works. Joins are always just joining rows together, and your WHERE clauses are only going to be looking at one row at a time (hence why your expectations are not working like you expect -- it's not possible for one row to have two values for the same column.
There are a bunch of ways to solve this when dealing with raw SQL, but in Rails, I've found the simplest (not most efficient) way is to embed subqueries using the EXISTS keyword. Wrapping that up in a solution which handles arbitrary number of desired att_ids, you get:
scope = att_ids_to_find.reduce(Product) do |relation, att_id|
relation.where('EXISTS (SELECT 1 FROM product_atts WHERE parent_id=products.id AND att_id=?)', att_id)
end
products = scope.all
If you're not familiar with reduce, what's going on is it's taking Product, then adding one additional where clause for each att_id. The end result is something like Product.where(...).where(...).where(...), but you don't need to worry about that too much. This solution also works well when mixed with scopes and other joins.
So I have been trying to create a dummy application to try and learn Rails. The app I thought I could create is a coffee ordering app for a group of people in work.
So the website will have many users.
A user can create a coffee_order.
A coffee order contains orders for other individual users.
Each user can have one or more coffee_shop_items (e.g. latte,
cappuccino,danish, muffin, etc)
A coffee order also has an assignee, this is the person who is tasked
with going and getting the order.
So as a user, I create a coffee order, select an assignee, add users to the order, and add one or more coffee shop items to each user,
I am really struggling with how the database should be, and what the associations need to be, along with any join tables?
I am also trying to use nested attributes for the form entry.
Thanks in advance for help.
Update with some code I have tried to create a coffee order:
#coffee_order = CoffeeOrder.new(coffee_order_params)
params[:coffee_order][:user_coffee_orders_attributes].each do |user_order|
order = #coffee_order.user_coffee_orders.new(user_id: user_order[1][:user_id].to_i)
user_order[1][:coffee_shop_items].each do |item|
coffee_shop_item = CoffeeShopItems.find(item) if item != ""
# this line fails! see error below
#coffee_order.user_coffee_orders.coffee_shop_items << coffee_shop_item if coffee_shop_item != nil
end
end
error:
NoMethodError (undefined method `coffee_shop_items' for #<UserCoffeeOrder::ActiveRecord_Associations_CollectionProxy:0x42c6180>):
The coffee_shop_items belong to the order, not the user. After all, a user could probably create another order another day? You should probably also check out the rails documentation, which, IIRC actually contains a walk-through of a shopping cart application.
User has_many :coffes_orders
User has_many :coffee_orders_he_needs_to_get, class_name: "CoffeeOrder", foreign_key: "assignee_id"
CoffeeOrder belongs_to :user
CoffeeOrder belongs_to :assignee, class_name: "User"
CoffeeOrder has_and_belongs_to_many :coffee_shop_items
Coffee_shop_items has_and_belongs_to_many :coffee_orders
In User model there is has_one relation to Professional. In the professional model I have one Array field named industries.
I need to take all values where professional industries in "IT"
I tried User.where(:"professional.industries".in => ["IT"])
But Its not working. Any sugestions..??
In order for your query to work you should use
class User
embeds_one :professional
end
If you are sure that Professional should be a separate collection you could use something like:
uids = Professional.where(:"industries".in => ["IT"]).distinct(:user_id)
users = User.where(:_id.in => uids)
I am using Rails v2.3.2.
I have a model called UsersCar:
class UsersCar < ActiveRecord::Base
belongs_to :car
belongs_to :user
end
This model mapped to a database table users_cars, which only contains two columns : user_id, car_id.
I would like to use Rails way to count the number of car_id where user_id=3. I konw in plain SQL query I can achieve this by:
SELECT COUNT(*) FROM users_cars WHERE user_id=3;
Now, I would like to get it by Rails way, I know I can do:
UsersCar.count()
but how can I put the ...where user_id=3 clause in Rails way?
According to the Ruby on Rails Guides, you can pass conditions to the count() method. For example:
UsersCar.count(:conditions => ["user_id = ?", 3])
will generates:
SELECT count(*) AS count_all FROM users_cars WHERE (user_id = 3)
If you have the User object, you could do
user.cars.size
or
user.cars.count
Another way would be to do:
UserCar.find(:user_id => 3).size
And the last way that I can think of is the one mentioned above, i.e. 'UserCar.count(conditions)'.
With the belogngs to association, you get several "magic" methods on the parent item to reference its children.
In your case:
users_car = UsersCar.find(1) #=>one record of users_car with id = 1.
users_car.users #=>a list of associated users.
users_car.users.count #=>the amount of associated users.
However, I think you are understanding the associations wrong, based on the fact that your UsersCar is named awkwardly.
It seems you want
User has_and_belongs_to_many :cars
Car has_and_belongs_to_manu :users
Please read abovementioned guide on associations if you want to know more about many-to-many associations in Rails.
I managed to find the way to count with condition:
UsersCar.count(:condition=>"user_id=3")
I need to find an elegant solution to scoped finds based on access control rules. Essentially I have the following setup:
Users
Customers
AccessControl - Defines which user has access to another users data
Users need to be able to access not just their own customers but also shared customers of other users.
Obviously something like a simple association will not work:
has_many :customers
and neither will this:
has_many :customers, :conditions => 'user_id in (1,2,3,4,5)'
because the association uses with_scope and the added condition is an AND condition not an OR condition.
I also tried overriding the find and method_missing methods with the association extension like this:
has_many :customers do
def find(*args)
#get the user_id and retrieve access conditions based on the id
#do a find based on the access conditions and passed args
end
def method_missing(*args)
#get the user_id and retrieve access conditions based on the id
#do a find based on the access conditions and passed args
end
end
but the issue is that I don't have access to the user object / parent object inside the extension methods and it just does not work as planned.
I also tried default_scope but as posted here before you can't pass a block to a default scope.
Anyhow, I know that data segmentation and data access controls have been done before using rails and am wondering if somebody found an elegant way to do it.
UPDATE:
The AccessControl table has the following layout
user_id
shared_user_id
The customer table has this structure:
id
account_id
user_id
first_name
last_name
Assuming the the following data would be in the AccessControl table:
1 1
1 3
1 4
2 2
2 13
and so on...
And the account_id for user 1 is 13 I need to be able to retrieve customers that can be best described with the following sql statement:
select * from customers where (account_id = 13 and user_id = null) or (user_id in (1,3,4))
Sorry if I've completely missed the point here but I'm not 100% sure of what you want to do. Is AccessControl a relationship between User and Customer? If so looks like you just need to setup a many-to-many relationship.
class User
has_and_belongs_to_many :customers
# or this if you need to store meta data in the join table
has_many :customers
has_many :access_controls
has_many :accessible_customers, through => :access_controls
end