I have been doing some searching around Google and this site for some ways to go about constructing some models for an application I am working on.
I plan to have Users and Teams. A user can join a team and one team only. A team can obviously have many users. Also, I want to add a 'leader' role inside the team that is assigned to the User who creates a Team but can later be passed on to another User who is already a part of that team.
I have seen some examples of models for something like this and saw a few like this:
class User < ActiveRecord::Base
has_one :team
has_many :memberships
end
class Membership < ActiveRecord::Base
belongs_to :user
belongs_to :team
end
class Team < ActiveRecord::Base
has_many :memberships
has_many :users, :through => :memberships
end
Why is the Membership model necessary? I have seen it in a few examples and I am not sure I quite follow the logic of why it is in there and what it is doing.
Also, if I did something like has_one :leader in the Team model and had the Leader model, would that be considered the best practice for determining a leader in a Team? It seems like a bit much to have an entire model/table for Leader.
The Memberships model is allowing for a many-to-many relationship there. It's acting as the join table. It would allow Users to belong to many Teams and Teams to have many Users.
Sounds like you just want a one-to-many though?
class User < ActiveRecord::Base
belongs_to :team
end
class Team < ActiveRecord::Base
has_many :users
end
I'll have to double check this part but you can use additional parameters to specify the models in your assocation if they don't match up with the name you need. So Team could have a leader that's just a User model.
class Team < ActiveRecord::Base
has_many :users
has_one :leader, :class_name => "User", :foreign_key => "user_id"
end
the rails guides page on associations has a good summary including the part about the :class_name and other options
http://guides.rubyonrails.org/association_basics.html#the-has_many-association
Related
I am trying to set up the model structure that has a User model Project model along with two join tables setup as has_many through to manage two specific aspects of the Project, ProjectManagers and ProjectMembers.
I can setup two has_and_belongs_to_many but it doesn't feel very railsy.
Right now, this is what I have and I'm unsure of how to proceed to use multiple has_many through (Project Manager, Project Member) both referencing User model.
Would a nested through be the way to go even if a Project Manager will not always be part of the Project User table?
project.rb
class Project < ApplicationRecord
has_many :project_members
has_many :users, through: :project_manager
end
user.rb
class User < ApplicationRecord
has_many :project_managers
has_many :users, through: :project_managers
end
project_manager.rb
class ProjectManager < ApplicationRecord
belongs_to :project
belongs_to :user
end
project_member.rb
class ProjectMember < ApplicationRecord
belongs_to :project
belongs_to :user
end
I don't see any problems with what you're doing. There are other options, but this approach should work as you want. Have you tried it? I'd do something like this.
class Project < ApplicationRecord
has_many :project_members
has_many :project_managers
has_many :members, through: :project_members, :class_name => User.to_s
has_many :managers, through: :project_manager, :class_name => User.to_s
end
Another approach, since the join tables are similar is to subclass them and add a type column to the join table. Not necessarily better than what you're doing.
You could also create a project_users table (don't separate members and managers) and include a "role" column. A scope on project_user.rb would bring back managers or members.
Personally, I would go with your approach. Managers will likely have different auth and have relationships with other objects. It's simpler to query and less likely to make a mistake.
And, I wouldn't recommend a has_and_belongs_to_many, you're likely to add other columns to the join table and you'll be glad you have the model.
I'm a relative beginner to Rails, but am learning as I go. I'm trying to create a Tournament Entry portal, where a team would enter players for a given tournament. I've done a bit of reading about associations, but am having some trouble wrapping my head around how to apply them in this instance.
As a basic overview:
One tournament, has many teams.
Each team has many players
Therefore one tournament also has many players (through the teams
entered)
Here's my code for this, but I'm not sure it's right because I'm unable to get any tournament_ids associated to players.
(tournament.rb)
class Tournament < ApplicationRecord
has_many :teams
has_many :players, :through => :teams
end
(team.rb)
class Team < ApplicationRecord
belongs_to :tournament
has_many :players
end
(player.rb)
class Player < ApplicationRecord
has_one :team
has_one :tournament, :through => :team
end
Within the Players table there is both team_id & tournament_id fields, however I'm only able to populate the team_id field through association when I try in console.
I'm wondering if there's something amiss with my associations.
The usage of 'belongs_to', 'has_many', 'has_one' depends on the data model in database of course.
If you have team_id foreign key in players table, then you need to define Player class as:
class Player < ApplicationRecord
belongs_to :team
has_one :tournament, :through => :team
end
In addition, I really believe that Tournament <-> Team should have many-to-many association (if team can participate in many tournaments of course). I would suggest adding model TeamTournament and define final model structure as:
class Tournament < ApplicationRecord
has_many :team_tournaments
has_many :teams, :through => :team_tournaments
has_many :players, :through => :teams
end
class TeamTournament < ApplicationRecord
belongs_to :team
belongs_to :tournament
end
class Team < ApplicationRecord
has_many :team_tournaments
has_many :tournaments, :through => :team_tournaments
has_many :players
end
the Player class should have belongs_to associations with Team and Tournament
class Player < ApplicationRecord
belongs_to :team
belongs_to :tournament
end
OK. I assume your question is about your models associations rather than how to set up association for getting tournament_id from player and so on. So I'll try to hand you some tips about your project and associations could be set up for it.
As I got your portal idea... You want the tournament to has many teams and the team to has many players. But then you want to get tournament_id from player. I believe you don't want to do that because in real life tournament indeed may "has" some players but every single player don't has to belong to some tournament. He can take part in many tournaments. So you don't need to set up association for that. Same thing with tournament and teams. But since team has the player he has to belong to that team. So you need association for that.
Wrapping up my setup for you will be like:
(tournament.rb)
class Tournament < ActiveRecord::Base
has_many :teams
end
(team.rb)
class Team < ActiveRecord::Base
has_many :players
end
(player.rb)
class Player < ActiveRecord::Base
belongs_to :team
end
And an example about how you can get the tournament where certain team take part in without the direct association:
team = Team.first # just take some team
Tournament.includes(:teams).where(teams: { id: team.id })
The same way you can achieve your other goals (get the tournament certain player belongs to and so on). But such cases don't need associations. Associations are needed when the object relates to another conceptually.
Not sure how to setup the tables and the relationships for what I'm trying to achieve. I thought I need a has_one through relationship but I saw a few posts advising against that.
What I'm trying to achieve is a shop creates a list of their services and their staff select the services they do from this list.
Here's what I have so far:
class User
has_many :staff
# user and shop have relationship via roles (not shown for simplicity)
end
class Shop
has_many :staff
has_many :services
# user and shop have relationship via roles (not shown for simplicity)
end
class Service
belongs_to :shop
has_many :staff through: :staff_services
end
class Staff
belongs_to :shop
belongs_to :user
has_many :services through: :staff_services
end
class StaffService
belongs_to :staff
# ? has_one :service through: :shop
# ? belongs_to :service
end
I'm not sure how to set the relationship for StaffServices so that a staff is only able to select services from the shop they are a staff member of.
Any help would be appreciated. Thanks!
If I understand you correctly you want a many-to-many associations between Staff and Services. I believe you want belongs_to :service in your StaffService table. This can be simplified to isolate the association you're working with as such:
class Service
has_many :staff, through: :staff_services
end
class Staff
has_many :services, through: :staff_services
end
class StaffService
belongs_to :staff
belongs_to :service
end
I don't mean to suggest the other associations you've got in your example are invalid or wrong in any way--I just wanted to show only the many-to-many part. The associations you already have up there between Shop & Staff, and Shop & Services will allow you to build scopes easily that will restrict the set of Staff and Services involved.
If you haven't already, I suggest giving the Rails Guide to Associations a careful read.
I would like to create a double entry table form according two models.
For now I'm able to create a simple table with the members of a communities
on the columns, I must add the informations of an other model, like this :
My models :
Community
has_many :memberships
Membership
belongs_to :user
belongs_to :community
User
has_many ::memberships
has_many :skills
Skill
belongs_to :user
belongs_to :community
I there some gem existing to make a double entry table or is it easier to make it from scratch? if so, how can I begin ?
It seems like you would benefit from a through relationship here.
Instead of referencing community directly from the skill table, you could do:
Skill
belongs_to :user
has_many :communities, :through => :user
On user, add:
has_many :communities, :through => :memberships
Wouldn't this get the link between skill and community that you would like?
As Jay mentioned, you would benefit from a has_many :through relationship, or maybe a has_and_belongs_to_many relationship; whether it's the actual solution we'll have to see:
#app/models/user.rb
Class user < ActiveRecord::Base
has_many :memberships
has_many :skill_users
has_many :skills, through: :skill_users
end
#app/models/skill_user.rb
Class SkillUser < ActiveRecord::Base
belongs_to :skill
belongs_to :user
end
#app/models/skill.rb
Class Skill < ActiveRecord::Base
has_many :skill_users
has_many :users, through: :skill_users
end
This will allow you to associate each user (note that members are different than users) with specific skills without using double-entries in your tables
Relational
The basis of what you're seeking can be found in Relational Databases
These work by storing data in single instances, and linking to other data through foreign_keys. These foreign keys are things such as user_id etc:
(more information here)
This means instead of populating the same data twice, it is correct to reference that data from other models, as required. This is where join models come in
Join Model
Join models allow you to "link" two pieces of data through a join model:
For you, it means storing your skills in its own model, and linking users with skills on a join model (I've called skill_user.rb). This means that you'll be able to call your user's skills like this:
#user.skills #-> goes through the join model
I'm in the process of trying to develop my first rails application and before I jump off into actually implementing my ideas, I was hoping I could get some help with my association planning.
My application is going to be an educational tool and I have some basic functionality that I need to implement. I want to have students that can register for and create courses. Within these courses, there will be one user who is the teacher and the rest are students. Within the course will be assignments that the teacher creates and that users are required to make a submission for. These are the basics. Eventually I want to add more functionality but as of now I just need the foundations set.
Here are my ideas so far on what the associations should look like:
class User < ActiveRecord::Base
has_many :enrollments
has_many :courses, :through => :enrollments
end
class Course < ActiveRecord::Base
has_many :enrollments
has_many :users, :through => :enrollments
end
class Enrollment < ActiveRecord::Base
belongs_to :user # foreign key - user_id
belongs_to :course # foreign key - course_id
end
However, I'm running into my wall of inexperience at the moment with how to appropriately handle the rest of the associations at this point. I could probably hack out something, but I'd prefer to do it as best as I can the first time.
How do I handle the associations related to assignments and submissions? Presumably a student's submission should belong_to them, but it is also specifically related to an assignment within the class. Assignments originate within a course, but are also closely tied to the user.
Finally, what's the best way to handle the relationships between a user and the class they create? A user creates a course. Does that course belong_to them? Should I just add a column to the course's table for storing the creator's id? Etc.
Thanks for the help.
Suggestion:
You might want to separate out your Teacher and Student models, since you're very likely to have different actions associated with each (and while they share some attributes, they really are different entities in your model, for example, you likely want just one teacher teaching in a course.)
You could derive both the Teacher model and the Student model from a User model that has the shared attributes and authentication.
Now to your questions:
If you'd like to keep the student that created the course associated, creator_id is the way I'd go. (If a teacher can create a course too, deriving Student and Teacher from a shared User model would help)
Assignments and Submissions:
You've pretty much defined it in words. Here is the code.
[If different students within a course could get different assignments, only then do you want to build a direct association between Student and Assignment, otherwise, use a through association]
class User < ActiveRecord::Base
has_many :enrollments
has_many :courses, :through => :enrollments
has_many :assignments, :through => :courses
has_many :submissions
end
class Course < ActiveRecord::Base
has_many :enrollments
has_many :users, :through => :enrollments
has_many :assignments
end
class Enrollment < ActiveRecord::Base
belongs_to :user # foreign key - user_id
belongs_to :course # foreign key - course_id
end
class Assignment < ActiveRecord::Base
belongs_to :course
has_many :submissions
end
class Submission < ActiveRecord::Base
belongs_to :assignment
belongs_to :user
end