Why is my party not being created and saved to the database? - ruby-on-rails

Question

I have my parameters whitelisted and when I look at the output of party_params I see that they are permitted but when I got to save the instance into the database it gives me a rollback transaction in the console. I've tried just create, create then save, new then save. Is there something I am missing?
#controller
class PartiesController < ApplicationController
def new
#party = Party.new
end
def create
#party = Party.create(party_params)
redirect_to party_path(#party)
end
private
def party_params
params.require(:party).permit(
:name,
:trainer_id,
:pokemon1_id
)
end
end
#model
class Party < ApplicationRecord
belongs_to :trainer
belongs_to :pokemon
validates :name, presence: true
end
#view
<h1>Create a New Pokemon Party</h1>
<p>Select 6 Pokemon</p>
<%= form_for(#party) do |f| %>
<label>Party Name:</label>
<%= f.text_field :name %><br>
<label>Trainer Name:</label>
<%= collection_select(:party, :trainer_id, Trainer.order(:id), :id, :name, include_blank: true) %><br>
<label>Pokemon:</label>
<%= collection_select(:party, :pokemon1_id, Pokemon.order(:id), :id, :nickname, include_blank: false) %><br>
<%= f.submit %>
<% end %>
#schema
create_table "parties", force: :cascade do |t|
t.string "name"
t.integer "pokemon1_id"
t.integer "trainer_id"
t.datetime "created_at", precision: 6, null: false
t.datetime "updated_at", precision: 6, null: false
end

Answer 1

Lets start with the models. If you want a party to be able to include multiple pokemon you need to place the foreign key in the other model:
class Party < ApplicationRecord
belongs_to :trainer
has_many :pokemons # references the pokemons.party_id column
end
class Pokemon < ApplicationRecord
belongs_to :party # pokemons needs a `party_id` column
end
class AddPartyToPokemons < ActiveRecord::Migration
def change
add_reference :pokemons, :party, null: false, foreign_key: true
remove_column :parties, :pokemon1_id
end
end
This is very simplefied and assumes that Pokemon is an individual Pokemon and not the entire species and can only belong to a single party. Otherwise you need a many-to-many assocation with a join table/model.
In your controller you need to check if creating the record was actually successful and respond accordingly:
class PartiesController < ApplicationController
def new
#party = Party.new
end
def create
#party = Party.new(party_params)
if #party.save
redirect_to #party
else
render :new
end
end
private
def party_params
params.require(:party).permit(
:name,
:trainer_id,
pokemon_ids: []
)
end
end
If the user input is invalid this will render the app/parties/new.html.erb view and respond with it.
While you could use pry or byebug to step into the controller and check the errors you want to display the validation errors to the user in the view anyways so that they know what to actually do to correct the form:
<h1>Create a New Pokemon Party</h1>
<p>Select 6 Pokemon</p>
<%= form_for(#party) do |f| %>
<% if #party.errors.any? %>
<div id="error_explanation">
<h2><%= pluralize(#party.errors.count, "error") %> prohibited this party from being saved:</h2>
<ul>
<% #article.errors.each do |error| %>
<li><%= error.full_message %></li>
<% end %>
</ul>
</div>
<% end %>
<%
# group labels and inputs in an element instead of abusing BR tags
# this lets you style the content with CSS
-%>
<div class="field">
<%# use f.label as it sets the `for=` attribute which is important for screen readers -%>
<%= f.label :name, 'Party Name:' %>
<%= f.text_field :name %>
</div>
<div class="field">
<%= f.label :trainer_id, 'Trainer Name:' %>
<%# call the helper on the form builder to bind the input to the model -%>
<%= f.collection_select(:trainer_id, Trainer.order(:id), :id, :name, include_blank: true) %>
</div>
<div class="field">
<%= f.label :pokemon_ids, 'Pokemon:' %>
<%# call the helper on the form builder to bind the input to the model -%>
<%= f.collection_select(:pokemon_ids, Pokemon.order(:id), :id, :nickname, include_blank: false, multiple: true) %>
</div>
<div class="actions">
<%= f.submit %>
</div>
<% end %>
Note f.collection_select(:pokemon_ids, ...). This is a special setter/getter is generated by has_many :pokemons.