Rails Associations - Strong Parameters Build - ruby-on-rails

Question

So I have to following models.
class Team < ActiveRecord::Base
belongs_to :user
has_and_belongs_to_many :players
accepts_nested_attributes_for :players
end
class Player < ActiveRecord::Base
has_many :statistics
has_and_belongs_to_many :teams
end
I wish to build a team that has players, these will be selected by the user. I can do this perfectly in the console by doing to following.
#user = User.find(10)
#team = #user.build_team(name: "MyTeam", points: 0)
#<Team team_id: nil, name: "MyTeam", points: 0, user_id: 10>
#team.players.build(name: "Messi")
#<Player player_id: nil, name: "Messi", role: nil>
#team.save
However I am really struggling passing parameters due to strong params. Here is my view
<%= form_for :team do |f| %>
<%= f.label :name %><br />
<%= f.text_field :name %>
<%= f.fields_for :players do |players| %>
<%= players.label :player_name %>
<%= players.text_field :name %>
<% end %>
<div><%= f.submit "Create Team" %></div>
<% end %>
I want to build the team using the team parameters and the players using the player parameters, however I cannot figure out how to get this working in the controller.
class TeamController < ApplicationController
before_action :authenticate_user!
def new
end
def create
#user = User.find(current_user.id)
#team = #user.build_team(team_params) #Just the team paramaters
#team = #team.players.build(player_params)# I want just the player params
#team.save
end
private
# I can add the player param as nested i.e. .permit(:name, :players => [:name])
# but then build_team complains about receiving an array.
def team_params
params.require(:team).permit(:name)
end
end
Any solutions welcome, as are any improvements.
EDIT - ADDED SCHEMA
create_table "players", primary_key: "player_id", force: true do |t|
t.string "name", limit: 50, null: false
t.string "role", limit: 30, null: false
end
create_table "players_teams", id: false, force: true do |t|
t.integer "player_id", null: false
t.integer "team_id", null: false
end
# players_teams is a Composite Primary Key, as instructed in the guides;
# also essential for targeting.
create_table "teams", primary_key: "team_id", force: true do |t|
t.string "name", limit: 200, null: false
t.integer "points", default: 0, null: false
t.integer "user_id", null: false
end
EDIT 2
Since this has not yet been answered I'll add more explanation as to what I am attempting.
The user has one team, I can build the team and the relationship is also built thanks to ActiveRecord. The users team then has many players and players have many teams, when I try to build this relationship the players table never changes, no relationship is created.
I feel I should stress again that the following works perfectly in the rails console
#user = User.find(10)
#team = #user.build_team(name: "MyTeam", points: 0)
#<Team team_id: nil, name: "MyTeam", points: 0, user_id: 10>
#team.players.build(name: "Messi")
#<Player player_id: nil, name: "Messi", role: nil>
#team.save
Team is set to accept nested parameters so I thought this would work.
#team = #user.build_team(team_params)
def team_params
params.require(:team).permit(:name, players_attributes: [:name, :role])
end
I believe this should build the players model and create the relationship however no player is ever inserted and no relationship built.

Answer 1

First make a few changes in the TeamsController as below:
class TeamController < ApplicationController
before_action :authenticate_user!
def new
## Set "#team" and build "players"
#team = current_user.build_team
#team.players.build
end
def create
#team = current_user.build_team(team_params)
if #team.save
## Redirect to teams show page
redirect_to #team, notice: 'Team was successfully created.'
else
## In case of any error while saving the record, renders the new page again
render action: 'new'
end
end
private
# I can add the player param as nested i.e. .permit(:name, :players => [:name])
# but then build_team complains about receiving an array.
def team_params
## Permit players_attributes
params.require(:team).permit(:name, players_attributes: [:id, :name])
end
end
After this, update the view as below:
<%# Changed "form_for :team" to "form_for #team" %>
<%= form_for #team do |f| %>
<%= f.label :name %><br />
<%= f.text_field :name %>
<%= f.fields_for :players do |player| %> <%# Changed "|players|" to "|player|" %>
<%= player.label :name %> <%# Changed "player_name" to "name" and "players" to "player" %>
<%= player.text_field :name %> <%# Changed "players" to "player" %>
<% end %>
<div><%= f.submit "Create Team" %></div>
<% end %>
Set an instance variable #team in new action and build the players for that #team.
Use #team instance variable as an argument for form_for in your view code.
I have also suggested a few tweaks in the create action, so you know if the team is saved or not.
And fixed the team_params method to permit the nested attributes of players.
UPDATE
Using #team as an argument to form_for method is resource-oriented style and much preferred way.
Read this pretty good description about usage of form_for to get a better idea.
You can still implement the required code while using :team but its not preferred way of doing it.
Example using :team:
<%= form_for :team do |f| %>
<%# ... %>
<%= f.fields_for :players, f.object.players.build do |player| %> <%# build the players for the team %>
<%# ... %>
<% end %>
<%# ... f.submit "Create Team" %>
<% end %>
fields_for in your case would iterate over players (#team.players) belonging to a particular team (#team). If there are no players then you won't see any fields for players in the form, which is why you build the players so you at least get some blank fields for players to input which is why when using accepts_nested_attributes_for you need to build the nested attributes. You can build them either at controller level(as shown in above suggested code) or within the form.
Example for "within the form":
<%= form_for #team do |f| %>
<%# ... %>
<%= f.fields_for :players, #team.players.build do |player| %> <%# build the players for #team %>
<%# ... %>
<% end %>
<%# ... f.submit "Create Team" %>
<% end %>

Answer 2

Normally you'd just do the nested attributes at once which will create the players through nested attributes e.g.
def create
#user = User.find(current_user.id)
#team = #user.build_team(team_params)
#team.save
end
def team_params
params.require(:team).permit(:name, :players => [:name])
end
If you're desperate to seperate them you should be able to do something like
def player_params
params.require(:team).permit(:name, :players => [:name])[:team][:players]
end
I.e. you're going to have to filter out just the players parameters

Answer 3

As I was literally going through the same issues this weekend, I would highly recommend using a nested_form.
You can find all the implementation details here: https://github.com/ryanb/nested_form

Answer 4

You are very close with what you had.
Just add the :id field to player_attributes params and it should work for you.
def team_params
params.require(:team).permit(:name, players_attributes: [:id, :name, :role])
end
You may want to check out the cocoon gem. It makes it a lot easier for handling the nested forms and allowing users to add/remove using JS.
If you also want to allow destroying, add a check box for the field _destroy on the player and add the key in players_attributes. Also update the model to allow destroying.
Model:
class Team < ActiveRecord::Base
belongs_to :user
has_and_belongs_to_many :players
accepts_nested_attributes_for :players, allow_destroy: true
end
Controller:
def team_params
params.require(:team).permit(:name, players_attributes: [:id, :_destroy, :name, :role])
end
View:
<%= f.fields_for :players do |player| %> <%# Changed "|players|" to "|player|" %>
<%= player.label :name %> <%# Changed "player_name" to "name" and "players" to "player" %>
<%= player.text_field :name %> <%# Changed "players" to "player" %>
<%= player.check_box :_destroy %> Delete
<% end %>