Rails 5 update has_many through associates models - ruby-on-rails

Question

I have following models
class TeamPlayer < ApplicationRecord
belongs_to :team
belongs_to :player
belongs_to :role
end
class Team < ApplicationRecord
has_many :team_players
has_many :players, :through => :team_players
end
class Role < ApplicationRecord
has_many :team_players
has_many :players, :through => :team_players
end
class Player < ApplicationRecord
has_many :team_players
has_many :teams, :through => :team_players
has_many :roles, :through => :team_players
end
Basically, I want to assign different roles to different players in a team.
id team_id player_id role_id
2 1 2 1
3 3 2 1
4 1 1 2
What should it look like in my teams_controller.rb to add new player with a role, to update a player with new role and to remove that player from my team?

Answer 1

This is only the start of a possible solution and it is pretty similar to what you have with some model and database validations added. Some of these validations ensure the uniqueness of every three-way relationship (FilledTeamRole), so either the error of attempting to create a duplicate record would need to be handled or you could filter the possible ids of each class that could be selected so that a duplicate cannot be created.
A complete solution would depend on what other associations you want between the Team, Player and Role classes other than one that requires all three. For example, do you want/need an association between Team and Player where a relationship exists between only those two classes without the necessity of a Role (TeamPlayer id: 1, team_id: 1, player_id: 1). If those relationships are desired, then additional code will be needed to achieve this, which I have and can provide as a suggestion.
As far as what your controller would look like, you could use the filled_team_roles controller (or perhaps create a dashboard controller), provide instance variables #teams, #players and #roles to populate drop-down menus for each class within a form to create the filled_team_roles relationship. You could also have additional forms within each of the other classes where, using two drop-downs instead of three with the third value the selected model id of the class whose controller the form is in (e.g. the edit action in the players_controller with drop-downs for team and role)
~/app/models/team.rb
class Team < ApplicationRecord
has_many :filled_team_roles, dependent: :destroy
validates :name, uniqueness: { scope: [:sport, :city] }
scope :by_name_asc, -> { order(name: :asc) }
end
~/app/models/player.rb
class Player < ApplicationRecord
has_many :filled_team_roles, dependent: :destroy
validates_uniqueness_of :ssn
scope :by_name_asc, -> { order(last_name: :asc, first_name: :asc) }
end
~/app/models/role.rb
class Role < ApplicationRecord
has_many :filled_team_roles, dependent: :destroy
validates_uniqueness_of :name
scope :by_name_asc, -> { order(name: :asc) }
end
~/app/models/filled_team_role.rb
class FilledTeamRole < ApplicationRecord
belongs_to :team
belongs_to :player
belongs_to :role
validates :team_id, presence: true
validates :player_id, presence: true
validates :role_id, presence: true
validates :team_id, uniqueness: { scope: [:player_id, :role_id] }
end
~/db/migrate/20170127041000_create_team.rb
class CreateTeam < ActiveRecord::Migration[5.0]
def change
create_table :teams do |t|
t.string :name
t.string :sport
t.string :city
t.string :state
t.string :country
t.timestamps null: false
end
add_index :teams, [:name, :sport, :city], unique: true
end
end
~/db/migrate/20170127041100_create_player.rb
class CreatePlayer < ActiveRecord::Migration[5.0]
def change
create_table :players do |t|
t.string :first_name
t.string :last_name, index: true
t.string :full_name_surname_first
t.string :ssn, index: { unique: true }
t.timestamps null: false
end
end
end
~/db/migrate/20170127041200_create_role.rb
class CreateRole < ActiveRecord::Migration[5.0]
def change
create_table :roles do |t|
t.string :name, index: { unique: true }
t.timestamps null: false
end
end
end
~/db/migrate/20170127051300_create_filled_team_role.rb
class CreateFilledTeamRole < ActiveRecord::Migration[5.0]
def change
create_table :filled_team_roles do |t|
t.timestamps null: false
t.references :team
t.references :role
t.references :player
end
add_index :filled_team_roles,
[:team_id, :player_id, :role_id],
unique: true,
name: 'index_filled_team_roles_unique_combination_of_foreign_keys'
end
end
~/db/seeds.rb
Team.create(name: 'Los Angeles Dodgers', sport: 'baseball', city: 'Los Angeles', state: 'CA', country: 'United States')
Team.create(name: 'New York Yankees', sport: 'baseball', city: 'New York', state: 'NY', country: 'United States')
Team.create(name: 'Chicago Cubs', sport: 'baseball', city: 'Chicago', state: 'IL', country: 'United States')
Team.create(name: 'St. Louis Cardinals', sport: 'baseball', city: 'St. Louis', state: 'MO', country: 'United States')
Player.create(first_name: 'Max', last_name: 'Walker', full_name_surname_first: 'Walker, Max', ssn: '123-45-6789')
Player.create(first_name: 'Homer', last_name: 'Winn', full_name_surname_first: 'Winn, Homer', ssn: '234-56-7890')
Player.create(first_name: 'Will', last_name: 'Steel', full_name_surname_first: 'Steel, Will', ssn: '345-67-8901')
Player.create(first_name: 'Lucky', last_name: 'Snag', full_name_surname_first: 'Snag, Lucky', ssn: '456-78-9012')
Role.create(name: 'pitcher')
Role.create(name: 'catcher')
Role.create(name: 'first baseman')
Role.create(name: 'second baseman')
Role.create(name: 'shortstop')
Role.create(name: 'third baseman')
Role.create(name: 'right fielder')
Role.create(name: 'center fielder')
Role.create(name: 'left fielder')
FilledTeamRole.create(team_id: 1, player_id: 1, role_id: 1)
FilledTeamRole.create(team_id: 2, player_id: 2, role_id: 2)
FilledTeamRole.create(team_id: 3, player_id: 3, role_id: 3)
FilledTeamRole.create(team_id: 4, player_id: 4, role_id: 4)