Is it possible to order the results of school.classrooms by the teacher's name? I want to do this directly in the association, and not a separate call.
class School < ActiveRecord::Base
has_many :classrooms
end
class Classroom < ActiveRecord::Base
belongs_to :school
belongs_to :teacher
end
class Teacher < ActiveRecord::Base
has_one :classroom
end
This should work if you are using rails 3.x
school.classrooms.includes(:teacher).order("teachers.name")
Related
I have 3 models: Topic, Post, Link.
class Topic < ActiveRecord::Base
has_many :posts
end
class Post < ActiveRecord::Base
has_many :links
belongs_to :topic
end
class Link < ActiveRecord::Base
belongs_to :post
end
I'd like to have counter_cache for forums on Link model.
How can I do this ?
Check out the counter_culture gem.
From the readme:
class Product < ActiveRecord::Base
belongs_to :sub_category
counter_culture [:sub_category, :category]
end
class SubCategory < ActiveRecord::Base
has_many :products
belongs_to :category
end
class Category < ActiveRecord::Base
has_many :sub_categories
end
In the above example, the Category model will keep an up-to-date counter-cache in the products_count column of the categories table.
The association between class are as below
class Level < ActiveRecord::Base
has_many :levels_users
end
class LevelsUser < ActiveRecord::Base
belongs_to :level
has_many :schedules
end
class Schedule < ActiveRecord::Base
belongs_to :levels_user
end
I know the value of level.id. How do I find all schedules belonging to that level.id. level.id is the id of one of the level. I tried something like this:
Level.find(level.id).levels_users.schedule
But it won't work.
You could use through property of has_many association.
class Level < ActiveRecord::Base
has_many :levels_users
has_many :schedules, through: :levels_users
end
Now you can use
level.schedules
Here is my models:
class User < ActiveRecord::Base
has_many :products
has_many :comments
end
class Product < ActiveRecord::Base
belongs_to :user
has_many :comments
end
class Comment < ActiveRecord::Base
belongs_to :user
belongs_to :product
end
I need to get comment records from current user products only
How do I do that? thanks
If we move the relationships to use a has_many: comments, through: products you can probably get what you're after:
class User < ActiveRecord::Base
has_many :products
has_many :comments, through: products
end
class Product < ActiveRecord::Base
belongs_to :user
has_many :comments
end
class Comment < ActiveRecord::Base
belongs_to :user
belongs_to :product
end
Now you can do user.comments.
The rails docs are here, which say:
A has_many :through association is often used to set up a many-to-many
connection with another model. This association indicates that the
declaring model can be matched with zero or more instances of another
model by proceeding through a third model. For example, consider a
medical practice where patients make appointments to see physicians.
I have four models
Bid Order User Printer
currently I cannot access the order through anything except User.
I would like to be able to do something of the sort bid.order but have yet to figure out the correct association. Any thoughts?
class Bid < ActiveRecord::Base
belongs_to :printer
end
class Order < ActiveRecord::Base
belongs_to :user
has_many :bids
end
class Printer < ActiveRecord::Base
has_many :orders, through: :bids
has_many :bids
end
class User < ActiveRecord::Base
has_many :orders
end
Both models must know about the relationship so you need to state that in the Bid model
class Bid < ActiveRecord::Base
belongs_to :printer
belongs_to :order
end
how can I get a weight of product through a Record model? As I know, possible to get all products of certain record but I cannot find out the way getting the weight of certain product.
class User < ActiveRecord::Base
has_many :eatings
end
class Eating < ActiveRecord::Base
belongs_to :user
has_many :records
end
class Record < ActiveRecord::Base
belongs_to :eating
end
class Product < ActiveRecord::Base
end
class WeightedProduct < ActiveRecord::Base
end
What relationships should have Record and Product models with WeightedProduct so user will be able to get weight of certain product through one line User.first.eatings.first.records.first.products.first.weight?
Looks like you're after this:
class Record < ActiveRecord::Base
belongs_to :eating
has_many :weighted_products
end
class Product < ActiveRecord::Base
has_many :weighted_products
end
class WeightedProduct < ActiveRecord::Base
belongs_to :record
belongs_to :product
end
Then User.first.eatings.first.records.first.weighted_products.first.weight
I think that should work but haven't tested.
it seems that each product has one weighted product, then in that case you should add
class Product < ActiveRecord::Base
has_one :weighted_product
end
class WeightedProduct < ActiveRecord::Base
belongs_to :product
end
and
class Record < ActiveRecord::Base
belongs_to :eating
has_many :products
end