Rails 4 self referential many to many relationships - ruby-on-rails

Question

I can't wrap my head around this any help would be appreciated. I went through many articles and other postings on here and I can't seem to get the results I'm looking for.
I have a User model and Team model.
Team Model has user_id and team_id
The user who creates the team will be user_id and users who are members of the team will be in the team_id
User Model
has_many :teams, foreign_key: :team_id
has_many :team_members, class_name: "Team", foreign_key: :user_id
Team Model
belongs_to :user, foreign_key: :team_id
belongs_to :team_member, class_name: "User", foreign_key: :user_id
The end result of what I'm trying to achieve is:
Each user can add as many team members
Each user can see a list of users who are part of their team.
A view where, Users who are part of a team can see which team they are part of.

Answer 1

I believe what you're looking for is a join table model. The issue is that both a User and a Team may have many of each other. So the relationship must be stored separately.
See this answer here on a similar question: https://stackoverflow.com/a/15442583/5113832
So you might choose a model structure of User, Team and TeamMembership.
Updated to destroy dependent team memberships when a user or team is destroyed.
#app/models/user.rb
class User < ActiveRecord::Base
has_many :team_memberships, :dependent => :destroy
has_many :teams, :through => :team_memberships
end
#app/models/team.rb
class Team < ActiveRecord::Base
has_many :team_memberships, :dependent => :destroy
has_many :users, :through => :team_memberships
end
#app/models/team_membership.rb
class TeamMembership < ActiveRecord::Base
belongs_to :user
belongs_to :team
end
Updated to reply to question:
How would my controller look on create? (Adding a user to a team) – Michael
In order to add a user to to a team you COULD do it in UserController, you COULD do it in TeamController. However, because you are now creating a TeamMembership resource you would want to create a TeamMembership record in a TeamMembershipsController. This keeps with the "Rails" way of doing things. So for example:
# app/controllers/team_memberships_controller.rb
class TeamMembershipsController < ApplicationController
def index
#team_memberships = TeamMembership.all
end
def new
#team_membership = TeamMembership.new
end
def create
#team_membership = TeamMembership.new(team_membership_params)
if #team_membership.save
flash[:success] = 'Team membership created'
redirect_to team_memberships_path
else
flash[:error] = 'Team membership not created'
render :new
end
end
def destroy
#team_membership = TeamMembership.find_by_id(params[:id])
if #team_membership && #team_membership.destroy
flash[:success] = 'Team membership destroyed'
else
flash[:error] = 'Team membership not destroyed'
end
redirect_to team_memberships_path
end
private
def team_membership_params
params.require(:team_membership).permit(
:user_id,
:team_id
)
end
end
The advantage to having the TeamMembership resource is using this pattern to manage when a user is added (#create), or removed (#destroy) from a team.
The magic of Rails associations will take care of accessing a team's members (users) and a user's teams for each instance of those models.
You just go about your business doing CRUD on these resources and Rails takes care of the organization for you by your conforming to it's conventions.
Also I updated my original model code to destroy team memberships when a user or team is destroyed. This ensures no orphaned records are in your team_memberships table.
As a final note. You should also be able to easily use form_for to send a TeamMembership to your controller to be created. This could be done using select option dropdowns for users and teams with Rails' collection_select:
<%# app/views/team_memberships/new.html.erb %>
<h1>
Create Team Membership
</h1>
<%= form_for(#team_membership) do |f| %>
<%= f.label(:user) %>
<%= f.collection_select(
:user_id,
User.all,
:id,
:username
) %>
<%= f.label(:team) %>
<%= f.collection_select(
:team_id,
Team.all,
:id,
:name
) %>
<%= f.submit %>
<% end %>
The above code will render dropdown for all users and teams allowing you to select a specific combination to create a team membership from. Deleting a team membership is as easy as sending a DELETE #destroy request with the id of the team membership.
Another consideration might be adding a unique pair constraint to your database table and model within the migration and model validations.
Hope this helps!