model-creation

name	model-creation
description	Create and modify Rails models following project conventions for STI, enums, validations, counter caches, and scopes
license	MIT

What I do

• Generate new models with bin/rails g model
• Set up STI hierarchies (Event → Tournament/League, Result → Win/Draw/Loss)
• Configure enum columns, counter caches, and associations
• Write validations using modern Rails 8 syntax ({ presence: true })
• Add scopes and class methods

When to use me

• Adding new domain models
• Adding STI children to existing hierarchies
• Modifying model associations or validations
• Adding enums or counter caches

Project Conventions

File Location

• Models: app/models/<name>.rb
• Concerns: app/models/concerns/
• STI children in same file or separate file

Model Skeleton

# frozen_string_literal: true

class ModelName < ApplicationRecord
  # Associations
  belongs_to :parent, optional: true
  has_many :children, dependent: :destroy

  # Enums
  enum :status, { draft: 0, active: 1 }, default: :draft

  # Validations (Rails 8 style)
  validates :field, { presence: true }
  validates :other, { uniqueness: { scope: :parent_id } }

  # Scopes
  scope :active, -> { where(status: :active) }

  # Callbacks (if needed)
  before_save :compute_slug
end

STI (Single Table Inheritance)

• Base class: Event < ApplicationRecord (type column: type)
• Subclass: Tournament < Event (no explicit type needed if base defaults)
• Type column in schema: t.string "type", default: "Tournament", null: false
• Subclass files: app/models/tournament.rb, app/models/league.rb
• STI children inherit base associations; override as needed
• Fixtures require explicit type: "Tournament" field

Enums

• Integer-backed: enum :state, { draft: 0, open: 1 }, default: :draft
• Prefixed enums: enum :play_mode, { scheduled: 0, pickup: 1 }, prefix: true
  • Generates play_mode_scheduled?, play_mode_pickup?, play_mode_scheduled!
  • Aliases: alias pickup_play_mode? play_mode_pickup?
• Enum validation via integer values in fixtures: state: 3

Counter Caches

• Declare: belongs_to :event, counter_cache: true
• Schema needs integer column: t.integer "event_participants_count", default: 0, null: false
• Reset in fixtures: set explicitly (counter caches not auto-set from fixtures)
• Call Event.reset_counters in test_helper.rb setup block

Validations (Rails 8)

• Hash-style: validates :name, { presence: true } — preferred over validates :name, presence: true
• With options: validates :field, { uniqueness: { scope: :parent_id } }
• Conditional: validates :other, { numericality: { greater_than: 0 }, allow_blank: true }
• Custom validations: validate :must_match_kind_with_category
• with_options presence: true do ... end for grouped presence

Associations

• belongs_to with optional: true when foreign key is nullable
• has_many ... dependent: :destroy for ownership
• has_many ... dependent: :nullify for soft references
• has_one ... dependent: :nullify for one-to-one
• through associations: has_many :players, through: :event_participants
• Scoped associations: has_many :results, -> { publishable }

Scopes

• Lambda scopes: scope :ongoing, -> { where(state: %i[swiss single_elimination]) }
• Order scopes: scope :ranked, -> { order(points: :desc) }
• Join scopes: scope :for_organizer, ->(organizer) { where(event_organizer: organizer) }
• Complex SQL scopes for existence checks
• Publishable scope pattern: joins(:parent).where.not(parents: { finished_at: nil })

Callbacks

• Prefer before_validation over before_save when value computation is needed
• after_update :action, if: -> { field_previously_changed? } for change-triggered actions
• before_save :reset_cache, if: -> { linked_previously_changed? }
• Use previously_changed? instead of was for Rails 8 compatibility

Active Record Patterns

• attribute :field, :type for typed attributes with defaults
• normalizes :field, with: ->(e) { e.strip.downcase } for normalization
• find_or_initialize_by for upsert patterns
• find_or_create_by for create-or-retrieve patterns
• update_columns for bypassing callbacks (use sparingly)

Key Files

• app/models/user.rb — Example: STI-like setup, callbacks, normalization
• app/models/event.rb — Example: counter caches, STI base, scopes
• app/models/infraction.rb — Example: enum hierarchy, custom validations
• app/models/league.rb — Example: prefixed enums, aliased predicates