require 'active_support/option_merger' class Object # An elegant way to factor duplication out of options passed to a series of # method calls. Each method called in the block, with the block variable as # the receiver, will have its options merged with the default +options+ hash # provided. Each method called on the block variable must take an options # hash as its final argument. # # Without with_options>, this code contains duplication: # # class Account < ActiveRecord::Base # has_many :customers, dependent: :destroy # has_many :products, dependent: :destroy # has_many :invoices, dependent: :destroy # has_many :expenses, dependent: :destroy # end # # Using with_options, we can remove the duplication: # # class Account < ActiveRecord::Base # with_options dependent: :destroy do |assoc| # assoc.has_many :customers # assoc.has_many :products # assoc.has_many :invoices # assoc.has_many :expenses # end # end # # It can also be used with an explicit receiver: # # I18n.with_options locale: user.locale, scope: 'newsletter' do |i18n| # subject i18n.t :subject # body i18n.t :body, user_name: user.name # end # # When you don't pass an explicit receiver, it executes the whole block # in merging options context: # # class Account < ActiveRecord::Base # with_options dependent: :destroy do # has_many :customers # has_many :products # has_many :invoices # has_many :expenses # end # end # # with_options can also be nested since the call is forwarded to its receiver. # # NOTE: Each nesting level will merge inherited defaults in addition to their own. # # class Post < ActiveRecord::Base # with_options if: :persisted?, length: { minimum: 50 } do # validates :content, if: -> { content.present? } # end # end # # The code is equivalent to: # # validates :content, length: { minimum: 50 }, if: -> { content.present? } # # Hence the inherited default for `if` key is ignored. # def with_options(options, &block) option_merger = ActiveSupport::OptionMerger.new(self, options) block.arity.zero? ? option_merger.instance_eval(&block) : block.call(option_merger) end end