ActiveRecord is Rotting Your Brian

ActiveRecord is Rotting Your Brain@ethangunderson Great Lakes Ruby Bash 2011

Order.all.select{ |order| order.status == ‘open’ } Order.all.slice(0, N).map(&:id)

Abstractions

“All non-trivialabstractions, tosome degree, areleaky.” - Joel Spolsky

The Law of Leaky Abstractions

Order.all.select{ |order| order.status == ‘open’ }

SELECT * FROM orders;Typecast each record returned into an ActiveRecord Order object.

Order.all.select{ |order| order.status == ‘open’ }

class Order < ActiveRecord::Base named_scope :open, where(:status => ‘open’)endOrders.openOrder.where(:status => ‘open’)

SELECT * FROM orders where status = ‘open’;

validates_uniqueness_of

User 1: Checksfor uniqueness User 2: Checks for uniquenessUser 1: Inserts record User 2: Inserts record

SolutionCreate a Unique Index

Law of Demeter

Each unit should have only limited knowledge about other units: onlyunits "closely" related to the current unit. Each unit should only talk to its friends; dont talk to strangers.Only talk to your immediate friends.

order.user.address.stree t

class Order < ActiveRecord::Base belongs_to :user delegate :street, :to => :userendclass User < ActiveRecord::Base has_one :address delegate :street, :to => :addressend

class Order < ActiveRecord::Base belongs_to :user def address_street user.address_street endendclass User < ActiveRecord::Base has_one :address def address_street address.street endend

N+1users = User.allusers.each do |user| user.address.streetend

1users = User.includes(:address).allusers.each do |user| user.address.streetend

N*OMGorders = Order.allorders.each do |order| order.item.name order.user.address.street order.item.merchant.name *end

orders = Order.includes(:user=> :address).allorders.each do |order| order.item.name order.user.address.street order.item.merchant.name *end

ActiveRecordAll Over The Place

Connascence

Connascence of NameConnascence of TypeConnascence of MeaningConnascence of PositionConnascence ofAlgorithmConnascence ofExecutionConnascence of TimingConnascence of Identity

Rule of DegreeConnascence of NameConnascence of TypeConnascence of MeaningConnascence of PositionConnascence of AlgorithmConnascence of ExecutionConnascence of TimingConnascence of Identity

order.update_attributes({ :status => ‘closed’ })

order.close!

Connascence of MeaningConnascence of Name

user = User.find(params[:user_id])user.orders.create(params[:order])

user = User.find(params[:user_id])user.add_order(params[:order])

current_user.orders.open.order(:created_at)

current_user.current_orders

The Database is Your Friend

github.com/trptcolin/consistency_fail

In your ~/.irbrc...if Object.const_defined?(ActiveRecord) ActiveRecord::Base.logger = Logger.new(STDOUT)end

https://github.com/dsboulder/ query_reviewer

Thanks!

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ActiveRecord is Rotting Your Brian

by Ethan Gunderson

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