Two classes:
class Investor
field :name
has_and_belongs_to_many :users
end
class User
field :name
has_and_belongs_to_many :investors
end
I already have users and investors I don't want to create new. What is the way of inclusing like
#user=User.first
#investor=Investor.first
#inves_sec=Investor.last
Now what is the way to add #investor and #invest_sec to the user investors id, all the command I found in mongoid doc create new investor object, I wasn't able to find thorugh which you can use existing object.
It's easy enough as you could do something like:
#first_investor = Investor.first
#user.investors.push(#first_investor)
There are a lots of examples here of various scenarios dealing with relationships/references.
Related
I'm trying to create an association for a beta meat-sale application between one model, Cuts, and the "animal_type" attribute of another model, Animal, such that I could list all the cuts associated with a particular animal_type (or associated with an animal that has that type as an attribute).
In other words, if animal_type is "cow", I should be able to call up a list of all the cuts (ribeye, tenderloin, etc) associated with cows. I'm new to Rails, and this is fairly above my head.
My idea was to create an animal_type column in Cuts and Animals, to associate each cut with a type of animal, so I could do something along the lines of
#cuts = Cut.where(:animal_type => Animal::animal_type[:Cow])
No idea if that works, though, and what else I need to do to make this association possible. Can anybody help point me towards a way of thinking this through? Or does anyone have any good resources I could look at to help me with this specific problem? I've been looking through Rails Guides, and they're helpful, but they don't really give me a way to answer this.
You could have a Cuts model and an Animal model. Cuts could have a string attribute called "name" which would store the cut type such as ribeye, tenderloin etc. Animal could have a string attribute called animal_type. You could then setup a has_many association between Animals and Cuts. Something like this:
class Animal < ActiveRecord::Base
attr_accessible :animal_type
has_many :cuts
end
class Cuts < ActiveRecord::Base
attr_accessible :name
belongs_to :animals
end
This should be a good start
I have a datamodel that contains a Project, which contains a list of Suggestions, and each Suggestion is created by a User. Is there a way that I can create a list of all distinct Users that made Suggestions within a Project?
I'm using Mongoid 3. I was thinking something like this, but it doesn't work:
#project = Project.find(params[:id])
#users = Array.new
#users.push(#project.suggestions.user) <-- this doesn't work
Any ideas? Here's my model structure:
class Project
include Mongoid::Document
has_many :suggestions, :dependent => :destroy
...
end
class Suggestion
include Mongoid::Document
belongs_to :author, class_name: "User", :inverse_of => :suggestions
belongs_to :project
...
end
class User
include Mongoid::Document
has_many :suggestions, :inverse_of => :author
...
end
While Mongoid can give MongoDB the semblance of relationships, and MongoDB can hold foreign key fields, there's no underlying support for these relationships. Here are a few options that might help you get the solution you were looking for:
Option 1: Denormalize the data relevant to your patterns of access
In other words, duplicate some of the data to help you make your frequent types of queries efficient. You could do this in one of a few ways.
One way would be to add a new array field to User perhaps called suggested_project_ids. You could alternatively add a new array field to Project called suggesting_user_ids. In either case, you would have to make sure you update this array of ObjectIds whenever a Suggestion is made. MongoDB makes this easier with $addToSet. Querying from Mongoid then looks something like this:
User.where(suggested_project_ids: some_project_id)
Option 2: Denormalize the data (similar to Option 1), but let Mongoid manage the relationships
class Project
has_and_belongs_to_many :suggesting_users, class_name: "User", inverse_of: :suggested_projects
end
class User
has_and_belongs_to_many :suggested_projects, class_name: "Project", inverse_of: :suggesting_users
end
From here, you would still need to manage the addition of suggesting users to the projects when new suggestions are made, but you can do so with the objects themselves. Mongoid will handle the set logic under the hood. Afterwards, finding the unique set of users making suggestions on projects looks like this:
some_project.suggesting_users
Option 3: Perform two queries to get your result
Depending on the number of users that make suggestions on each project, you might be able to get away without performing any denormalization, but instead just make two queries.
First, get the list of user ids that made suggestions on a project.
author_ids = some_project.suggestions.map(&:author_id)
users = User.find(author_ids)
In your Project class add this :
has_many :users, :through => :suggestions
You'll then be able to do :
#users.push(#project.users)
More info on :through here :
http://api.rubyonrails.org/classes/ActiveRecord/Associations/ClassMethods.html#method-i-has_many
For mongoid, take a look at this answer :
How to implement has_many :through relationships with Mongoid and mongodb?
I made a relationship with the three models using has_many :through:
class Curriculum class < ActiveRecord::Base
has_many :interests
has_many :vacancies,: through => :interests
end
class Vacancy class < ActiveRecord::Base
has_many :interests
has_many :resumes,: through => :interests
end
class Interest < ActiveRecord:: Base
belongs_to :vacancy
belongs_to :curriculum
end
And to create curriculum and vacancy, I create them by administrative, i need to know how can i create the interest to the id of the vacancy, and how it will be logged on the system I have to get the id of it and make the relationship in creating a new bank interest. I wonder how I can program it to do so, and I wonder how the controller will get the create action, and what better way to do this.
First, try to read the whole "Guide to Rails on Associations", especially the part about has_many :through. Then check your schema if your db is migrated and contains for the table interests the necessary foreign keys to curriculums and vacancies called curriculum_id and vacancy_id.
If that is all in place, the following code will create the relationship between two objects:
#curr = Curriculum.find(1)
#vac = Vacancy.find(1)
#curr.interests << #vac
#curr.save
The last two lines creates an interest between #curr and #vac and store that on the database. So you should not use IDs and handle them directly, but work with objects instead.
The second part now is to provide a UI to allow the definition (and removal) of interests between curricula and vacancies. The base flow here is:
You have one curriculum in focus.
You have a link to add / remove curricula.
The view that opens shows a list of possible vacancies, where every vacancy has a checkbox.
By selecting (or deselecting) the check boxes, the IDs of the vacancies will be held in the params of the request sent to the controller.
See the (older) podcast Railscast #52 how to do that in a similar context. Or see the example for has_many :through with checkboxes.
An alternative way would be to use JQuery autocomplete, and add so interests one-by-one. See the nice podcast Railscast #258 which uses JQuery Tokeninput for that.
I think this is what your looking for:
HABTM Checkboxes
That's the best way to use an Has and Belongs to many association.
Im building an app where Users have some sort of wishlist
a User can have only one wishlist, and can add existing Items to that wishlist
however the Items belong to other Users on the site
I need to be able to access the wishlist items through current_user.wishlist.items (im using Devise so current_user is available)
i though of adding a wishlist_id column to the items table, but that wouldnt work since items can belong to multiple wishlists.
this seems simple but im having a hard time visualizing the relationship or the migration im supposed to generate
class User < ActiveRecord::Base
has_one :wishlist # or belongs_to :wishlist, it depends which you prefer
end
class Wishlist < ActiveRecord::Base
belongs_to :user
has_and_belongs_to_many :items
end
And of course:
./script/rails generate migration create_item_wishlists wishlist_id:integer item_id:integer
to create join table between items and wishlists.
UPDATE: To answer "frank blizzard" question in comment:
Let's say you have the same structure as in my answer (just change Item to Product or other model name), with HABTM relationship you just need to add new "item" to collection of "items", and then save wishlist:
#user.wishlist.items << item
#user.wishlist.save
You can make it method in user:
class User
def add_to_wishlist(item)
wishlist.items << item
end
end
If you want to remove or modify collection of "items", just use any Ruby method from Array and then save wishlist, which will check differences for you and save only changes.
Say if #news_writers is an array of records. I then want to use #news_writers to find all news items that are written by all the news writers contained in #news_writers.
So I want something like this (but this is syntactically incorrect):
#news = News.find_all_by_role_id(#news_writers.id)
Note that
class Role < ActiveRecord::Base
has_many :news
end
and
class News < ActiveRecord::Base
belongs_to :role
end
Like ennen, I'm unsure what relationships your models are supposed to have. But in general, you can find all models with a column value from a given set like this:
News.all(:conditions => {:role_id => #news_writers.map(&:id)})
This will create a SQL query with a where condition like:
WHERE role_id IN (1, 10, 13, ...)
where the integers are the ids of the #news_writers.
I'm not sure if I understand you - #news_writers is a collection of Role models? If that assumption is correct, your association appears to be backwards - if these represent authors of news items, shouldn't News belong_to Role (being the author)?
At any rate, I would assume the most direct approach would be to use an iterator over #news_writers, calling on the association for each news_writer (like news_writer.news) in turn and pushing it into a separate variable.
Edit: Daniel Lucraft's suggestion is a much more elegant solution than the above.