Rails ActiveRecord Scopes

equipment.rb

# app/models/equipment.rb

class Equipment < ApplicationRecord
  has_many :requests
  has_many :customers, through: :requests

  validates :brand, presence: true
  validates :model, presence: true
  validates :equipment_type, presence: true
  validates :serial_no, presence: true
  validates :accessories, presence: true

  # Default Scope
  default_scope {order("updated_at desc")}

  default_scope {where("available = ?", true)}

  # Named Scope
  scope :not_available, -> { where("available = ?", false)}
  scope :available, -> {where("available = ?", true)}

  # Named Scope with Arguments
  scope :not_available, ->(bool) {where("available = ?", bool)}

  # Chaining Scopes
  scope :available_and_created, -> {available.order(:created_at)}

  # Scope with Conditional
  scope :available, -> (bool){where("available = ?", bool) if bool.present? }

  # Calling multiple scopes in a class method scope
  def self.chaining(multiple_method)
    multiple_method.inject(self, :send)
  end
end

# Using Named Scope

# equip = Equipment.all
# equip.not_available

# Using Unscoped

# equip = Equipment.first
# equip unscoped

# Using Chaining Scope

# Equipment.brand.is_available

# Using multiple scopes in a class method Scope

# Equipment.chaining(["scope_one", "scope_two"])

equipments_controller.rb

# app/controllers/equipment_controller.rb

class EquipmentsController < ApplicationController
  def index
    @equip = Equipment.is_available
    render json: @equip, status: 200
  end

  # Or

  def index
    @equips = Equipment.all
    render json: @equips, status: 200
  end

  def availability
    @equip = Equipment.is_available
    render json: @equip, status: 200
  end

  # Or

  def index
    if params[:equipment]
      args = params[:equipment][:multiple_method]
      @equip = Equipment.chaining(args)
    else
      @equip = Equipment.all
    end
  end
end

notes.md

Scoping allows us to make use of commonly-used queries which can be referenced as method calls on the association objects or models,

The general expectation is that all scope bodies should return an ActiveRecord::Relation or nil. As a result of this, it makes it easy to call other ActiveRecord methods on it. Simply put, a scope is just a custom chain of active record methods. They are sets of pre-defined queries that can be chained to build other complex Queries.

Default Scopes vs Named Scopes

• Default scopes take the name default_scope when defined in the model and, they are scopes that are applied across all queries to the model in question.

• When it comes to which scope type to use, please avoid using default_scopes https://dev.to/lewuathe/why-we-should-avoid-defaultscope-in-rails-3ofo