Simplify object and association checks

* check for <object> instead of <object>.nil?
* check for <association>_id? instead of <association>.nil? (avoids
  record loading)

app/models/quantity.rb

@@ -7,8 +7,8 @@ class Quantity < ApplicationRecord
     dependent: :restrict_with_error
 
   validate if: ->{ parent.present? } do
-    errors.add(:parent, :user_mismatch) unless user == parent.user
+    errors.add(:parent, :user_mismatch) unless user_id == parent.user_id
-    errors.add(:parent, :self_reference) if self == parent
+    errors.add(:parent, :self_reference) if id == parent_id
   end
   validate if: ->{ parent.present? }, on: :update do
     errors.add(:parent, :descendant_reference) if ancestor_of?(parent)
@@ -68,7 +68,7 @@ class Quantity < ApplicationRecord
       numbered.project(
         numbered[Arel.star],
         numbered.cast(numbered[:child_number], 'BINARY').as('path'),
-      ).where(root.nil? ? numbered[:parent_id].eq(nil) : numbered[:id].eq(root.id)),
+      ).where(root ? numbered[:id].eq(root.id) : numbered[:parent_id].eq(nil)),
       numbered.project(
         numbered[Arel.star],
         arel_table[:path].concat(numbered[:child_number]),

app/models/unit.rb

@@ -6,9 +6,9 @@ class Unit < ApplicationRecord
   has_many :subunits, class_name: "Unit", inverse_of: :base, dependent: :restrict_with_error
 
   validate if: ->{ base.present? } do
-    errors.add(:base, :user_mismatch) unless user == base.user
+    errors.add(:base, :user_mismatch) unless user_id == base.user_id
-    errors.add(:base, :self_reference) if self == base
+    errors.add(:base, :self_reference) if id == base_id
-    errors.add(:base, :multilevel_nesting) if base.base.present?
+    errors.add(:base, :multilevel_nesting) if base.base_id?
   end
   validates :symbol, presence: true, uniqueness: {scope: :user_id},
     length: {maximum: type_for_attribute(:symbol).limit}

app/views/default/units/_unit.html.erb

@@ -1,5 +1,5 @@
 <%= tag.tr do %>
-  <td class="<%= class_names({subunit: unit.base, grayed: unit.default?}) %>">
+  <td class="<%= class_names({subunit: unit.base_id?, grayed: unit.default?}) %>">
     <%= unit %>
   </td>
 

app/views/quantities/create.turbo_stream.erb

@@ -3,5 +3,5 @@
 <% @ancestors.map do |ancestor| %>
   <%= turbo_stream.replace ancestor %>
 <% end %>
-<%= @before.nil? ? turbo_stream.append(:quantities, @quantity) :
+<%= @before ? turbo_stream.before(@before, @quantity) :
-  turbo_stream.before(@before, @quantity) %>
+  turbo_stream.append(:quantities, @quantity) %>

app/views/quantities/new.turbo_stream.erb

@@ -8,11 +8,11 @@
 
 <%= turbo_stream.append :quantity_form do %>
   <%- tabular_form_with model: @quantity, html: {id: ids[:form_tag]} do |form| %>
-    <%= form.hidden_field :parent_id unless @quantity.parent.nil? %>
+    <%= form.hidden_field :parent_id if @quantity.parent_id? %>
   <% end %>
 <% end %>
 
-<% if @quantity.parent %>
+<% if @quantity.parent_id? %>
   <%= turbo_stream.remove ids[:row] %>
   <%= turbo_stream.after @quantity.parent, partial: 'form', locals: ids %>
 <% else %>

app/views/quantities/reparent.turbo_stream.erb

@@ -5,5 +5,5 @@
   <%= turbo_stream.replace ancestor %>
 <% end %>
 <% @self_and_progenies.each do |q| %>
-  <%= @before.nil? ? turbo_stream.append(:quantities, q) : turbo_stream.before(@before, q) %>
+  <%= @before ? turbo_stream.before(@before, q) : turbo_stream.append(:quantities, q) %>
 <% end %>

app/views/units/_form.html.erb

@@ -2,16 +2,14 @@
   <%- tag.tr id: row, class: "form", onkeydown: "processKey(event)",
     data: {link: link, form: form_tag, hidden_row: hidden_row} do %>
 
-    <td class="<%= class_names({subunit: @unit.base}) %>">
+    <td class="<%= class_names({subunit: @unit.base_id?}) %>">
       <%= form.text_field :symbol, required: true, autofocus: true, size: 12 %>
     </td>
     <td>
       <%= form.text_area :description, cols: 30, rows: 1, escape: false %>
     </td>
     <td class="number">
-      <% unless @unit.base.nil? %>
+      <%= form.number_field :multiplier, required: true, size: 10, min: :step if @unit.base_id? %>
-        <%= form.number_field :multiplier, required: true, size: 10, min: :step %>
-      <% end %>
     </td>
 
     <td class="actions">

app/views/units/_unit.html.erb

@@ -14,7 +14,7 @@
 
   <% if current_user.at_least(:active) %>
     <td class="actions">
-      <% if unit.base.nil? %>
+      <% unless unit.base_id? %>
         <%= image_link_to t('.new_subunit'), 'plus-outline', new_unit_path(unit),
           id: dom_id(unit, :new, :link), onclick: 'this.blur();', data: {turbo_stream: true} %>
       <% end %>

app/views/units/create.turbo_stream.erb

@@ -1,4 +1,4 @@
 <%= turbo_stream.close_form dom_id(@unit.base || Unit, :new) %>
 <%= turbo_stream.remove :no_items %>
-<%= turbo_stream.replace @unit.base unless @unit.base.nil? %>
+<%= turbo_stream.replace @unit.base if @unit.base_id? %>
-<%= @before.nil? ? turbo_stream.append(:units, @unit) : turbo_stream.before(@before, @unit) %>
+<%= @before ? turbo_stream.before(@before, @unit) : turbo_stream.append(:units, @unit) %>

app/views/units/destroy.turbo_stream.erb

@@ -1,3 +1,3 @@
-<%= turbo_stream.replace @unit.base unless @unit.base.nil? %>
+<%= turbo_stream.replace @unit.base if @unit.base_id? %>
 <%= turbo_stream.remove @unit %>
 <%= turbo_stream.append(:units, render_no_items) if current_user.units.empty? %>

app/views/units/new.turbo_stream.erb

@@ -8,11 +8,11 @@
 
 <%= turbo_stream.append :unit_form do %>
   <%- tabular_form_with model: @unit, html: {id: ids[:form_tag]} do |form| %>
-    <%= form.hidden_field :base_id unless @unit.base.nil? %>
+    <%= form.hidden_field :base_id if @unit.base_id? %>
   <% end %>
 <% end %>
 
-<% if @unit.base %>
+<% if @unit.base_id? %>
   <%= turbo_stream.remove ids[:row] %>
   <%= turbo_stream.after @unit.base, partial: 'form', locals: ids %>
 <% else %>

app/views/units/rebase.turbo_stream.erb

@@ -1,4 +1,4 @@
 <%= turbo_stream.remove @unit %>
-<%= turbo_stream.replace @previous_base unless @previous_base.nil? %>
+<%= turbo_stream.replace @previous_base if @previous_base %>
-<%= turbo_stream.replace @unit.base unless @unit.base.nil? || @previous_base == @unit.base %>
+<%= turbo_stream.replace @unit.base if @unit.base_id? && (@previous_base.id != @unit.base_id) %>
-<%= @before.nil? ? turbo_stream.append(:units, @unit) : turbo_stream.before(@before, @unit) %>
+<%= @before ? turbo_stream.before(@before, @unit) : turbo_stream.append(:units, @unit) %>

app/views/units/update.turbo_stream.erb

@@ -1,3 +1,3 @@
 <%= turbo_stream.close_form dom_id(@unit, :edit) %>
-<%= turbo_stream.replace @unit.base unless @unit.base.nil? %>
+<%= turbo_stream.replace @unit.base if @unit.base_id? %>
 <%= turbo_stream.replace @unit %>