I'm currently working on a small project using Ruby On Rails 3.2 to create a database that contains several unique Models. Each Model has many Elements and each Element has the potential to belong to many Models. I have been able to set up the models in the following manner:
class Model < ActiveRecord::Base
has_many :model_elements
has_many :elements, :through => :model_elements
attr_accessible :elements, :name, :notes, :ref
end
class Element < ActiveRecord::Base
has_many :model_elements
has_many :models, :through => :model_elements
attr_accessible :elementType, :name, :notes, :ref
validates_presence_of :name
end
class ModelElement < ActiveRecord::Base
belongs_to :Model
belongs_to :element
attr_accessible :model_id, :created_at, :element_id
end
My question is how do I add multiple Elements to a single Model? I've tried to find some documentation but I can't find anything. Currently I'm trying to do the following:
#model.elements = #element
Where #element is a predefined element however it's throwing the following error:
undefined method `each' for #<Element:0x007ff803066500>
Any help would be greatly appreciated.
Try
#model.elements << #element
collection.create(attributes = {})
Returns a new object of the collection type that has been instantiated with attributes, linked to this object through the join table, and that has already been saved.
#model.elements.create(:name => "example")
Amar's answer is correct. If you wanted you can simplify your models further by using the has_and_belongs_to_many association.
class Model < ActiveRecord::Base
has_and_belongs_to_many :elements, :join_table => :model_elements
end
class Element < ActiveRecord::Base
has_and_belongs_to_many :models, :join_table => :model_elements
end
#model.elements << #element
Related
I have a parent model called Quote. which has an attribute called final_quote and has a child model called QuoteBoms, which has attributes called quote_final_quote and quantity and total_quote (=quote_final_quote * quantity)
class Quote < ActiveRecord::Base
has_many :quote_boms, dependent: :destroy
accepts_nested_attributes_for :quote_boms, :reject_if => :all_blank, :allow_destroy => true
class QuoteBom < ActiveRecord::Base
belongs_to :quote
has_many :quotes
end
Now in the nested model, I am selecting the quote with the association "belongs_to :quote" but has_many :quotes does not work as I have only one quote_id column (I suppose this is the problem). I see that i need to define a third class as quotebom_quote_id but cannot figure out how exactly!
Any help will be greatly appreciated!
class Image < ActiveRecord::Base
belongs_to :imageable, :polymorphic => true
end
class Profile < ActiveRecord::Base
has_many :images, :as => :imageable
end
class Article < ActiveRecord::Base
has_many :images, :as => :imageable
end
This is how we have made a single Image model and it is accessed by one or more than one model
Please refer this
Link
From what I can tell, you wish to create a database structure containing the models Quote and QuoteBom where a Quote has many QuoteBom and QuoteBom belongs to many Quotes.
That being the case, you will want to use a has_and_belongs_to_many association.
This will require adding to your models
class Quote < ActiveRecord::Base
has_and_belongs_to_many :quote_boms
end
class QuoteBom < ActiveRecord::Base
has_and_belongs_to_many :quotes
end
...and the following migration (assuming Quote and QuoteBom already exist)
class CreateQuotesAndQuoteBoms < ActiveRecord::Migration
def change
create_table :quote_quote_boms, id: false do |t|
t.belongs_to :quote, index: true
t.belongs_to :quote_bom, index: true
end
end
end
By having the associations above in the model and this table in your database, rails will automagically handle the associations between quote and quote_doms. As a result, you will also be able to access quote_dom.quotes which you said you weren't able to do in your question.
This is NOT a polymorphic association. A polymorphic association allows a model to belong to more than one type of other model in a single association.
I have created two models(User, Project) with many to many associations and create a association table(ProjectUser):
class User < ActiveRecord::Base
attr_accessor :name, :email
has_many :project_users
has_many :projects, through: :project_users
end
class Project < ActiveRecord::Base
attr_accessor :name, :address
has_many :project_users
has_many :users, through: :project_users
end
class ProjectUser < ActiveRecord::Base
belongs_to :project
belongs_to :user
end
With association specified, I can get a user's projects like this:
projects = User.find('user_id').projects
While if I just want project name list, is there any method works like this:
# This will get NoMethod error
project_names = User.find('user_id').projects.names
Now I do it like this:
project_names = User.find('user_id').projects.map {|project| project.name}
I'm wondering is there any syntactic sugar to do like this :)
If all you want is the names you should be able to do a join on the project_users table and simply pluck the names:
project_names = Project.joins(:project_users).where(user_id: 'user_id').pluck(:name)
If you already have the user then I'd just do it through the association like you have.
#user = User.find(params[:id])
project_names = #user.projects.pluck(:name)
More info on pluck here
I have the following models:
class Productmainclass < ActiveRecord::Base
attr_accessible :name, :id, :maintext
has_many :producttaggings, :dependent => :destroy
has_many :products, :through => :producttaggings
has_many :productsubclasses
end
class Productsubclass < ActiveRecord::Base
attr_accessible :name, :id, :maintext
has_many :producttaggings, :dependent => :destroy
has_many :products, :through => :producttaggings
belongs_to :productmainclass
end
class Product < ActiveRecord::Base
attr_accessible :name, :productimage, :size, :description, :price
has_many :producttaggings, :dependent => :destroy
has_many :productsubclasses, :through => :meteoritetaggings
has_many :productmainclasses, :through => :meteoritetaggings
mount_uploader :productimage, ProductimageUploader
end
class Producttagging < ActiveRecord::Base
belongs_to :product
belongs_to :productsubclass
belongs_to :productmainclass
attr_accessible :product_id, :productsubclass_id, :productmainclass_id
end
I now want to create a Product with FactoryGirl and Capybara. In the spec I simply have:
product = FactoryGirl.create(:product)
In my factories.rb I have:
factory :product do
name "Blue glass"
description "Description text of product"
productimage File.new(File.join(::Rails.root.to_s, "spec/factories/", "testimage.jpg"), 'rb')
productsubclass
productmainclass
end
factory :productsubclass do
name "Colored glasses"
productmainclass
end
factory :productmainclass do
name "Glasses"
end
Running the test I get:
Failure/Error: product = FactoryGirl.create(:product)
NoMethodError:
undefined method `productsubclass=' for #<Product:0xcd42090>
I think the way you have it setup would work if you were dealing with a situation where :product belonged to productsubclass, then the product and the productsubclass would be created with the product.productsubclass_id nicely inserted and all would be fine, but that's clearly not your structure, so we'd have to use another way. I think the link that #depa noted is the right way to go, specifically the 'Basic has many associations' section in this document: http://robots.thoughtbot.com/aint-no-calla-back-girl although you have the added complexity of a has_many through. But essentially your looking at a situation where you create an object and then after that you trigger another create to make the many's. Hope this makes sense :)
** Update **
Here's another approach which might be a little limited but you could just create the records from the other direction. So, if you just want one record in each object/table how about this:
FactoryGirl.define do
factory :producttagging do
product
productsubclass
productmainclass
end
end
I just can't figure out how to create a relation with a join table. I've read all the posts about them, but the main error seems to be that in the join table to models should be singular, which I have. I just can seem to create the models correctly and assign them. I have projects with datasets, and projects can have multiple datasets, while a dataset can belong to multiple projects. A dataset can be active or not, which is why I need the has_many through instead of the has_many_and_belongs_to setup.
My model definitions are:
class Project < ActiveRecord::Base
attr_accessible :name, :user_id
belongs_to :user
has_many :activedatasets
has_many :datasets, :through => :activedatasets
end
class DataSet < ActiveRecord::Base
attr_accessible :name, :project_id, :filename, :tempfilename
has_many :activedatasets
has_many :projects, :through => :activedatasets
end
class ActiveDataSet < ActiveRecord::Base
attr_accessible :active, :data_set_id, :project_id
belongs_to :project
belongs_to :dataset
end
When I create a new dataset I've got the project_id in the params, so I'm trying to setup the relationship like below:
class DataSetsController < ApplicationController
def new
#dataset = DataSet.new
#dataset.activedatasets.project_id = params[:project_id]
end
end
The error I'm getting seems famous:
NameError in DataSetsController#new
uninitialized constant DataSet::Activedataset
Can anybody point me in the right direction please?
Thanks for you attention.
You need to use:
has_many :active_data_sets
has_many :data_sets, :through => :active_data_sets
And in the DataSet model:
has_many :active_data_sets
has_many :projects, :through => :active_data_sets
Basically, rails expects you to use underscores to separate words in association names, and converts them to CamelCase. So active_data_sets becomes ActiveDataSet. Rails then uses this to work out which model class the association is with.
You also need to change your controller to this:
class DataSetsController < ApplicationController
def new
#dataset = DataSet.new
#dataset.active_data_sets.build(:project_id => params[:project_id])
end
end
Otherwise you'll get an error because you tried to set the project_id of the active_data_sets collection rather than creating a new ActiveDataSet.
I am newbie to Ruby on Rails and trying to learn this hard way , by writing my own project.
I have scenario where a test contain many problems, and problems can be reused in other tests also. So I have created models something like this.
class Test < ActiveRecord::Base
has_many :test_problems
has_and_belongs_to_many :problems
has_many :problems, :through => :test_problems
belongs_to :user
attr_accessible :name, :user_id, :reusable
end
class Problem < ActiveRecord::Base
belongs_to :user
has_many :test_problems
has_and_belongs_to_many :tests
has_many :tests, :through => :test_problems
attr_accessible :name, :statement, :input, :output, :user_id , :reusable
end
class TestProblem < ActiveRecord::Base
belongs_to :test
belongs_to :problem
attr_accessible :problem_id, :test_id
end
Now I have tested I can correctly add the association in Test Controller create after save.
#test.problems << Problem.find( :last )
I am looking for way how can user add many problems to his test when he create new one. I am unable to write the view and controller code handling this. What javascript are required. First a solution is good and then how can proceed to optimize this using partial extra would be great.
-Hemant