Rails has_many :through nested forms with simple form - ruby-on-rails

Question

I am trying to make a player character generator. I have a form that hopefully will allow me to attach skills with their values to a character sheet model. I made models like this:
class CharacterSheet < ApplicationRecord
has_many :character_sheet_skills, dependent: :destroy
has_many :skills, through: :character_sheet_skills
belongs_to :user
accepts_nested_attributes_for :skills
end
class Skill < ApplicationRecord
has_many :character_sheet_skills, dependent: :destroy
has_many :character_sheets, through: :character_sheet_skills
attr_reader :value
end
class CharacterSheetSkill < ApplicationRecord
belongs_to :skill
belongs_to :character_sheet
end
Character sheet model holds data about player character and skill model has all skills available in game. In CharacterSheetSkill I'd like to store the skills that the player chooses for his character together with an integer field setting the skill value.
When opening form, I already have a full list of skills in database. All I want to do in form is create a character sheet that has all of these skills with added value. I tried using "fields_for" in form, but I couldn't really get that to work. Right now it looks like this:
<%= simple_form_for [#user, #sheet] do |f| %>
<%= f.input :name %>
<%= f.input :experience, readonly: true, input_html: {'data-target': 'new-character-sheet.exp', class: 'bg-transparent'} %>
...
<%= f.simple_fields_for :skills do |s| %>
<%= s.input :name %>
<%= s.input :value %>
<% end %>
<% end %>
How can I make that form so it saves character sheet together with CharacterSheetSkills?

Answer 1

A better idea here is to use skills as a normalization table where you store the "master" definition of a skill such as the name and the description.
class CharacterSheetSkill < ApplicationRecord
belongs_to :skill
belongs_to :character_sheet
delegate :name, to: :skill
end
You then use fields_for :character_sheet_skills to create rows on the join table explicitly:
<%= f.fields_for :character_sheet_skills do |cs| %>
<fieldset>
<legend><%= cs.name %></legend>
<div class="field">
<%= cs.label :value %>
<%= cs.number_field :value %>
</div>
<%= cs.hidden_field :skill_id %>
</fieldset>
<% end %>
Instead of a hidden fields you could use a select if you want let the user select the skills.
Of course nothing will show up unless you "seed" the inputs:
class CharacterSheetController < ApplicationController
def new
#character_sheet = CharacterSheet.new do |cs|
# this seeds the association so that the fields appear
Skill.all.each do |skill|
cs.character_sheet_skills.new(skill: skill)
end
end
end
def create
#character_sheet = CharacterSheet.new(character_sheet_params)
if #character_sheet.save
redirect_to #character_sheet
else
render :new
end
end
private
def character_sheet_params
params.require(:character_sheet)
.permit(
:foo, :bar, :baz,
character_sheet_skill_attributes: [:skill_id, :value]
)
end
end