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Project Notes

Rails AntiPatterns

Book notes - Rails AntiPatterns by Chad Pytel and Tammer Saleh, published by Addison-Wesley Professional.


I devoured Rails AntiPatterns back in the day (it was published in 2010), and the advice it offers has stood the test of time.

Table of Contents - Highlights

1. Models

voyeristic models

  • problem: models know too much about the entire system
  • solution: law of demeter
    • principle of least knowledge
    • not make indirect calls
    • use only one dot
  • solution: push all find() calls into finders on the model
  • solution: keep finders on their own model

fat models

  • problem: many methods in a single model class
  • solution: delegate responsibility to new classes
  • solution: use modules
  • solution: reduce the size of large transaction blocks

spaghetti SQL

  • problem: using SQL instead of AR capabilities
  • solution: use AR associations and finders effectively
  • solution: learn and love the scope method
  • solution: use full-text search
    • ferret, sphinx, solr, xapian

duplicate code duplication

  • problem:models not DRY
  • solution: extract into modules
  • solution: write a plugin/gem
  • solution: meta-programming

2. Domain Modeling

authorization astronaut

  • problem: authorization nuilt into user model helper methods
  • solution: simplify with simple flags (roles has flags)

million model march

  • problem: model bloat
  • solution: denormalise into text fields
  • solution: use rails serialization



  • problem: too much code in the view template
  • solution: use standard helpers
  • solution: add useful accessors to your models
  • solution: extract to custom helpers
    • can also use a decorator (*)

markup mayhem

  • problem: non-semantic markup
  • solution: use rails helpers
  • solution: use haml

4. Controllers

homemade keys

  • problem: custom authentication schemes
  • solution: use clearance/device/authlogic…

fat controller

  • problem: business logic in the controller
  • solution: use AR callbacks and setters
  • solution: move to presenter
    • plain ruby class that orchestrates creation of multiple models

bloated sessions

  • problem: too much data in cookies/session store
  • solution: store references instead of instances

monolithic controllers

  • problem: many non-RESTful actions
  • solution: embrace REST

controller with many faces

  • problem: controller takes on some non-RESTful responsibilities
  • solution: refactor non-RESTful actions into another controller

lost child controller

  • problem: child model instances created without parent
  • solution: use nested resources

rats nest resources

  • problem: controllers that work as both nested and not
  • solution: use separate controllers for each nesting
    • or IR optional parents

evil twin controllers

  • problem: not DRY across different controllers that work on same model
  • solution: use rails 3 responders

5. Services

fire and forget

  • problem: make external call and ignore the response
  • solution: know what exceptions to look out for

sluggish services

  • problem: external apps too slow
  • solution: set your timeouts
  • solution: move task to background

pitiful page parsing

  • problem: web scraping
  • solution: use a gem e.g.
    • nokogiri
    • rest_client

successful failure

  • problem: errors sent back as HTTP 200 response
  • solution: obey HTTP status codes

kraken code base

  • problem: code base growing very large
  • solution: divide into confederated applications

6. Using Third-party Code

Recutting the gem

  • problem: repeated requirements across many projects
  • solution: look for a gem first

amateur gemologist

  • problem: can’t assume an existing gem is suitable
  • solution: follow TAM
    • check for tests
    • check for activity
    • check for maturity

vendor junk drawer

  • problem: fail to keep the number of gems manageable
  • solution: prune irrelevant or unused gems

miscreant modification

  • problem: gem has bugs or needs extension
  • solution: consider vendored code sacrosanct
    • monkey patch
    • fork
    • share and share-alike

7. Testing

Fixture blues

  • problem: fixtures are fragile, imported to db without validation, skip AR lifecycle
  • solution: make use of factories
  • solution: refactor into contexts

lost in isolation

  • problem: mocking obscures actual behaviour
  • solution: watch your integration points
    • ensure integraiton tests cover unit tests that use mocks

mock suffocation

  • problem:
  • solution:

untested rake

  • problem: rake tasks not tested
  • solution: extract to class method

unprotected jewels

  • problem: extracting to gem/plugin need tests too
  • solution: write normal unit tests without rails
  • solution: load only the parts of rails you need
  • solution: break out the atom bomb (include ful rails in your tests)

8. Scaling & Deploying

scaling roadblocks

  • problem: initial work is scale limited
  • solution: build to scale from the start
    • head in the clouds (e.g. paperclip can support S3)
    • file system limits
    • deploy to clustered env from start (e.g. heroku)

disappearing assets

  • problem: fixed assets must not be moved during deployment (e.g. with capistrano)
  • solution: make use of system directory (capistrano provided)

sluggish SQL

  • problem: sql performance issues
  • solution: add indexes
  • solution: reassess your domain model

painful performance

  • problem: slow response
  • solution: don’t do in ruby what you can do in SQL
  • solution: move processing into background jobs
  • solution:

9. Databases

messy migrations

  • problem: over time become a tangle of code
  • solution: never modify the up method of a committed migration
  • solution: never use external code in a migration
  • solution: always provide a down method (and run up/down to verify)

wet validations

  • problem: db attempts to enforce rails validations
  • solution: eschew constraints in the db (exceptions e.g. boolean)

10. Building for Failure

continual catastrophe

  • problem: lurking failure modes
  • solution: fail fast

inaudible failures

  • problem: failures don’t bubble or report
  • solution: never fail quietly
    • embrace the !
    • never rescue nil
    • log to a useful place (e.g. airbrake)

Credits and References

About LCK#97 rubyrailsbook
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This page is a web-friendly rendering of my project notes shared in the LittleCodingKata GitHub repository.

LittleCodingKata is my collection of programming exercises, research and code toys broadly spanning things that relate to programming and software development (languages, frameworks and tools).

These range from the trivial to the complex and serious. Many are inspired by existing work and I'll note credits and references where applicable. The focus is quite scattered, as I variously work on things new and important in the moment, or go back to revisit things from the past.

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