I'm creating an app that has a User and a Plugin model. A user can have multiple plugins and a plugin can belong to multiple users, which I've implemented using a junction table.
class Plugin < ActiveRecord::Base
has_many :user_plugins
has_many :users, through: :user_plugins
end
class User < ActiveRecord::Base
has_many :user_plugins
has_many :plugins, through: :user_plugins
end
class UserPlugins < ActiveRecord::Base
belongs_to :user
belongs_to :plugin
end
However, I then want to store arbitrary data for each user plugin (for example, things like api keys, options etc that can differ for each plugin.).
My initial approach was to have a user_plugins_options that joined on user_plugins, but I can't seem to get this to work correctly.
class UserPluginOptions < ActiveRecord::Base
belongs_to :user_plugins
end
My question, how should I go about approaching this to best work with ActiveRecord?
I think you misnamed your class, as the table is user_plugins but the model is UserPlugin. It’s plausible you are running into issues because of this.
Agree with Alex. Why don’t you create a json field on UserPlugin called options and keep a hash of plugin specific values here.
If you must have another table, you should add a has_one :user_plugin_option to your UserPlugin
Related
I have two models User and Project which are in has_and_belongs_to_many association
The user model has a column status
i can access the status of a user who is in project like
project.user.status
but a user can be in different projects i want his status to be on project level instead of on his id
If I understand your question correctly, the problem is that you need to associate the status of the user to one of potentially many projects that the user is associated with, but you are associating a single status to a single user instead of the project.
In that event, you need to abstract this association to an additional model, for instance "UserProjectStatus" which would be associated with both the User and the Project. You can do this using the has_many, through association. This would end up with something along the lines of:
class Project < ApplicationRecord
has_many :user_project_statuses
has_many :users, through :user_project_statuses
end
class UserProjectStatus < ApplicationRecord
belongs_to :user
belongs_to :project
end
class User < ApplicationRecord
has_many :user_project_statuses
has_many :projects, through :user_project_statuses
end
There is a good overview of this any many other Rails ActiveModel associations at https://guides.rubyonrails.org/association_basics.html#the-has-one-through-association.
Hope this helps!
I have many to many relation between users and projects through user_project. I know I could simply add has_many :projects in User Serializer (and vice versa in project serializer) to nest projects inside users.
But I also have a few additional fields in user_projects table (eg. start and end dates for user's participation in a corresponding project) and I have no idea what is the correct way to include them in the returned json. Should I create a special serializer for projects that are returned inside user with start_date included as a project's attribute or there's another way to do that?
The best way to do this would be to establish a 'has-many-through' (HMT) relationship between the user and project models and create a serializer for relationship's model.
class UserProjectSerializer < ActiveModel::Serializer
...
end
This will then be used in the UserSerializer via:
has_many :users_projects
The reason is that the relationship between the models contains additional data.
To implement the HMT, you'll need to create the user_projects model and define the HMT relationship in the related models:
users_project.rb
class UserProjects < ActiveRecord::Base
belongs_to :user
belongs_to :project
end
user.rb
class User < ActiveRecord::Base
has_many: users_projects
has_many: projects, through: :user_projects
end
project.rb
class Project < ActiveRecord::Base
has_many: users_projects
has_many: users, through: :user_projects
end
I have had a similar problem before and I made use of rabl. There is a good tutorial on railscasts to help you get started.
I'm trying to make a relationship where a model, Information, belongs_to either a User or a Client.
I thought about putting in my Information.rb
belongs_to :user
belongs_to :client
and in User.rb and Client.rb
has_one :information
But that makes it so that an information could belong_to both a User and a Client.
Is there a way to make it so that it can only belong to either or without just leaving one of the fields blank?
P.S. If it is needed I'm using Rails 4.2, Ruby 2.2.1, and Devise for my account authentication.
Thanks!
This sounds like an unusual association but it's a good fit for Polymorphic Association. In this case, you would declare a name for this association
class Information < ActiveRecord::Base
belongs_to :informational, polymorphic: true #or something like it
class User < ActiveRecord::Base
has_many informations, as :informational
class Client < ActiveRecord::Base
has_many informations, as :informational
And you would also need to add two columns to Information
informational_id, :integer and informational_type, :string
and Client and User need a integer called informational_id that is indexed.
I am trying to implement a resume feature and I was wondering the best practice for handling it. Lets assume a user has 2 pieces to a resume, education and work experience, and this is constant among all users. Then under each I want to save titles of things they've done (eg. Attended school at ______, worked at ________, project doing _______). Within these I want to save a description of that specific activity. What would be the best practice for implementing this?
So I need some association like: a user has_many experiences. An experience has_many titles. A title has_many descriptions. I also need to make the title of the experience is associated with the correct header (education or work experience).
I'm still pretty new to rails, and I'm sure there is a much easier and intuitive way to do this. Thanks for the help!
You can try these simple models structure for
class User < ActiveRecord::Base
has_many :locations
has_many :projects, through: experience_projects
end
class Location < ActiveRecord::Base
belongs_to :user
end
class Experience < ActiveRecord::Base
#experiences table should contain title and descriptions
belongs_to :user
has_many :projects, through: experience_projects
end
Now Join model if you do not require this intervention model you can directly use has_and_belongs_to_many
class ExperienceProject < ActiveRecord::Base
belongs_to :user
belongs_to :experience
end
I am trying to create an association between two tables. A student table and a computer table.
A computer can only ever be assigned to one student (at any one time) but a student can be assigned to multiple computers.
This is what I currently have in mind. Setting up a has-many through relationship and modifying it a bit.
class Student < ActiveRecord::Base
has_many :assignemnts
has_many :computers, :through => :assignments
end
class Computer < ActiveRecord::Base
has_one :assignment
has_one :student, :through => :assignments
end
class Assignment < ActiveRecord::Base
belongs_to :student
belongs_to :computer
end
Does this seem like the best way to handle this problem? Or something better sound out quickly to the experts here. Thanks!
You need first to decide if a simple one-to many relationship is enough for you.
If yes, it gets a lot easier, because you can get rid of the Assignment-class and table.
Your database-table "computers" then needs a student_id column, with a non-unique index
Your models should look like this:
class Computer < ActiveRecord::Base
belongs_to :student
end
class Student < ActiveRecord::Base
has_many :computers, :dependent => :nullify
end
"dependent nullify" because you don't want to delete a computer when a student is deleted, but instead mark it as free.
Each of your computers can only be assigned to a single student, but you can reassign it to a different student, for example in the next year.
Actually your approach is fine, as one offered by #alexkv. It is more discussion, than question.
Another thing if you want to use mapping table for some other purposes, like storing additional fields - then your approach is the best thing. In has_many :through table for the join model has a primary key and can contain attributes just like any other model.
From api.rubyonrails.org:
Choosing which way to build a many-to-many relationship is not always
simple. If you need to work with the relationship model as its own
entity, use has_many :through. Use has_and_belongs_to_many when
working with legacy schemas or when you never work directly with the
relationship itself.
I can advise you read this, to understand what approach better to choose in your situation:
http://api.rubyonrails.org/classes/ActiveRecord/Associations/ClassMethods.html
http://blog.hasmanythrough.com/2006/4/20/many-to-many-dance-off
You can also use has_and_belongs_to_many method. In your case it will be:
class Student < ActiveRecord::Base
has_many :assignemnts
has_and_belongs_to_many :computers, :join_table => 'assignments',
end
class Computer < ActiveRecord::Base
has_one :assignment
has_and_belongs_to_many :student, :join_table => 'assignments',
end
or you can rename assignments table to computers_students and remove join_table
class Student < ActiveRecord::Base
has_many :assignemnts
has_and_belongs_to_many :computers
end
class Computer < ActiveRecord::Base
has_one :assignment
has_and_belongs_to_many :student
end