Rails: Create action not saving has_many through associations - "rollback transaction" - ruby-on-rails

Question

Be easy on me, I'm just starting to learn Rails and this is my first question on here!
The project I'm using to learn is a volleyball scoreboard, so right now I'm trying to build a form that will submit the score of a 2v2 game. I have users and games which are associated by a has_many through relationship to a join table of participants which also includes a 'result' attribute ('W' or 'L').
My problem is that when I submit it fails, and no participants are created. If I removed the associations from the form, submission will work with just game parameters.
Hopefully, I've included all the relevant information below. Also, if there is a better way to do all this, I'd love to hear it!
MODELS
class Game < ApplicationRecord
has_one :venue
has_many :participants
has_many :users, through: :participants
accepts_nested_attributes_for :participants,
reject_if: :all_blank, allow_destroy: true
end
class User < ApplicationRecord
has_many :participants
has_many :games, through: :participants
end
class Participant < ApplicationRecord
belongs_to :game
belongs_to :user
end
SCHEMA
create_table "games", force: :cascade do |t|
t.date "game_date"
t.integer "winning_score"
t.integer "losing_score"
t.text "notes"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
t.integer "venue_id"
t.index ["venue_id"], name: "index_games_on_venue_id"
end
create_table "participants", force: :cascade do |t|
t.integer "user_id"
t.integer "game_id"
t.string "result"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
t.index ["game_id"], name: "index_participants_on_game_id"
t.index ["user_id"], name: "index_participants_on_user_id"
end
create_table "users", force: :cascade do |t|
t.string "name"
t.string "email"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
t.string "password_digest"
t.string "remember_digest"
t.index ["email"], name: "index_users_on_email", unique: true
end
create_table "venues", force: :cascade do |t|
t.string "name"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
end
CONTROLLER
class GamesController < ApplicationController
def show
#game = Game.find(params[:id])
end
def new
#users = User.all
#game = Game.new
#game.participants.build
end
def create
#game = Game.new(game_params)
if #game.save
redirect_to 'show'
else
render 'new'
end
end
private
def game_params
params.require(:game).permit(:game_date, :winning_score,
:losing_score, :notes, :venue_id,
participants_attributes: [:user_id, :result,
:_destroy])
end
end
FORM
<%= simple_form_for #game do |f| %>
<div id="winners">
<b>Winners</b>
<% for i in 0..1 %>
<%= f.simple_fields_for :participants do |p| %>
<%= p.association :user, :collection => #users, label: false %>
<%= p.input :result, :as => :hidden, :input_html => { :value => 'W' }%>
<% end %>
<% end %>
</div>
<%= f.input :winning_score, :collection => 15..30 %>
<div id="losers">
<b>Losers</b>
<% for i in 2..3 %>
<%= f.simple_fields_for :participants do |p| %>
<%= p.association :user, :collection => #users, label: false %>
<%= p.input :result, :as => :hidden, :input_html => { :value => 'L' }%>
<% end %>
<% end %>
</div>
<%= f.input :losing_score, :collection => 0..30 %>
<%= f.input :notes %>
<%= f.submit "Submit!", class: "btn btn-primary" %>
<% end %>
RESPONSE
Processing by GamesController#create as HTML
Parameters: {"utf8"=>"✓", "authenticity_token"=>"p8081+wU7EqYV7PIIAOGP3N+Md4CJusFpL9qTm3CeC54fP7pTPEwtfYS5v5x+ErBWxGiB0oj1pklYGXwl/cRBw==", "game"=>{"participants_attributes"=>{"0"=>{"user_id"=>"3", "result"=>"W"}, "1"=>{"user_id"=>"2", "result"=>"W"}, "2"=>{"user_id"=>"1", "result"=>"W"}, "3"=>{"user_id"=>"6", "result"=>"W"}}, "winning_score"=>"18", "losing_score"=>"4", "notes"=>"13241234"}, "commit"=>"Submit!"}
(0.1ms) begin transaction
User Load (0.1ms) SELECT "users".* FROM "users" WHERE "users"."id" = ? LIMIT ? [["id", 3], ["LIMIT", 1]]
User Load (0.0ms) SELECT "users".* FROM "users" WHERE "users"."id" = ? LIMIT ? [["id", 2], ["LIMIT", 1]]
User Load (0.0ms) SELECT "users".* FROM "users" WHERE "users"."id" = ? LIMIT ? [["id", 1], ["LIMIT", 1]]
User Load (0.1ms) SELECT "users".* FROM "users" WHERE "users"."id" = ? LIMIT ? [["id", 6], ["LIMIT", 1]]
(0.1ms) rollback transaction
Rendering games/new.html.erb within layouts/application
Rendered games/new.html.erb within layouts/application (69.4ms)
Rendered layouts/_shim.html.erb (0.4ms)
Rendered layouts/_header.html.erb (0.7ms)
Rendered layouts/_footer.html.erb (0.3ms)
Completed 200 OK in 199ms (Views: 144.9ms | ActiveRecord: 0.5ms)

Answer 1

#kkulikovskis comment worked for me. I changed:
has_many :participants
to
has_many :participants, inverse_of: :game
in the game model