An Introduction to Trailblazer

Steve BrudzLead Consultant @ Cyrus Innovation

@SteveBrudz / github.com/sbrudzMarch 8th, NYC.rb Meetup

#trbrb

The Challenge: Managing Complexity

Complexity by Mark Skipper via Flickr CC BY 2.0

Common Symptoms

• New features are hard to estimate• People are afraid to touch parts of the code• New developers take a long time to ramp up• Code is hard to unit test• CI build is brittle and takes forever• Big classes with many responsibilities• Hard to know where to put new logic• …

Every Application Faces It

Rails MVC

Best Practices

• Too much logic in your view?

- Bryan Helmkamp, Brian Vanloo, James Golick, and many others

Best Practices

• Too much logic in your view?– Put it in a view model insteadt

- Bryan Helmkamp, Brian Vanloo, James Golick, and many others

Best Practices

• Too much logic in your view?– Put it in a view model instead

• Too much logic in your controller?

- Bryan Helmkamp, Brian Vanloo, James Golick, and many others

Best Practices

• Too much logic in your view?– Put it in a view model instead

• Too much logic in your controller?– Put it in a form object, a policy object, or a service

object instead

- Bryan Helmkamp, Brian Vanloo, James Golick, and many others

Best Practices

• Too much logic in your view?– Put it in a view model instead

• Too much logic in your controller?– Put it in a form object, a policy object, or a service

object instead• Too much logic in your model?

- Bryan Helmkamp, Brian Vanloo, James Golick, and many others

Best Practices

• Too much logic in your view?– Put it in a view model instead

• Too much logic in your controller?– Put it in a form object, a policy object, or a service

object instead• Too much logic in your model?– Put it in a service object or a value object instead– t

- Bryan Helmkamp, Brian Vanloo, James Golick, and many others

Encapsulate Related Logic

• View Model• Form Object• Service Object• Policy Object• Value Object• Query Object• …

Benefits• Small classes• Easier to unit test• Easier to understand• Single responsibility

Great!

Great!But there are so many options

which do I choose…and how do I know if I’m on the right track…

Great!But there are so many options

which do I choose…and how do I know if I’m on the right track…

Wait, isn’t there a gem for that?

Trailblazer

An architectural layer for ruby-based web applications

Trailblazer

A set of Gems to help with implementing these patterns

Trailblazer

With clear conventions for where to put your logic

Trailblazer

And extensive documentation

https://leanpub.com/trailblazer http://trailblazer.to/

Trailblazer

A set of Gems to help with implementing these patterns

Trailblazer

A set of Gems to help with implementing these patterns

Trailblazer

A set of Gems to help with implementing these patterns

An Example

• A User can only view and edit their own Accounts• New Accounts should belong to the User that created them• An Account must have a name

Rails MVC

Trailblazer

GET /accounts/1

Traditional Rails controllers/accounts_controller.rb

GET /accounts/1

Trailblazer controllers/accounts_controller.rb

GET /accounts/1

Trailblazer concepts/account/read.rb

GET /accounts/1

Trailblazer concepts/account/policy.rb

GET /accounts/newPOST /accounts

Traditional Rails controllers/accounts_controller.rb

GET /accounts/newPOST /accounts

Trailblazer controllers/accounts_controller.rb

GET /accounts/newPOST /accounts

Trailblazer concepts/account/create.rb

GET /accounts/newPOST /accounts

Trailblazer spec/concepts/account/create_spec.rb

GET /accounts/newPOST /accounts

Trailblazer concepts/account/policy.rb

GET /accounts/newPOST /accounts

Trailblazer concepts/account/contract.rb

GET /accounts/newPOST /accounts

Trailblazer concepts/account/contract.rb

GET /accounts/newPOST /accounts

Traditional Rails models/account.rb

GET /accounts/newPOST /accounts

Trailblazer models/account.rb

GET /accounts/newPOST /accounts

Traditional Rails views/accounts/show.html.erb

GET /accounts/newPOST /accounts

Trailblazer views/accounts/show.html.erb

New Requirements

As a user, I should be able to:• View all transactions for an account• See my current and available balance• See a visual indicator for pending transactions• See the category for each transaction• See a flag for uncategorized transactions• …

New Requirements

Account Summary Page

Account Summary Page

Traditional Rails views/accounts/show.html.erb

Account Summary Page

views/accounts/show.html.erb

Trailblazer

Account Summary Page

Trailblazer concepts/account/cell.rb

Account Summary Page

Trailblazer concepts/account/views/show.erb

Account Summary Page

Trailblazer concepts/account/row_cell.rb

Account Summary Page

Trailblazer

concepts/account/views/row_cell.erb

Account Summary Page

The Cool Stuff

• Operations orchestrate complex business logic• Policies cleanly handle authorization• Cells manage complexity in the view layer• Reform enables editing multiple models at once• Representable and ROAR for APIs• Testability• Great documentation with clear patterns• Supportive community

The Not-so-Cool Stuff

• The learning curve• ReForm objects with nested properties can be

finicky• Partial use of Trailblazer can make app harder

to understand• Sharing model namespace can sometimes

cause weird TypeErrors (Account::Create shares Account < ActiveRecord::Base)

When and where to use Trailblazer?

• New projects that will need to scale• Existing large projects that use patterns

inconsistently• Existing projects that need only part of it

Thank you

• Cyrus Innovation• Nick Sutterer (@apotonick) • The Trailblazer community

Cyrus Innovation

• If you need help with getting your Rails app under control, come talk to us:

http://www.cyrusinnovation.com/contact/

• We’re hiring, too:http://www.cyrusinnovation.com/careers/current-openings/

Trailblazer Resources

• http://trailblazer.to• https://leanpub.com/trailblazer• https://gitter.im/trailblazer/chat

Articles Referenced

• http://blog.codeclimate.com/blog/2012/10/17/7-ways-to-decompose-fat-activerecord-models/

• https://www.toptal.com/ruby-on-rails/top-10-mistakes-that-rails-programmers-make

• http://jamesgolick.com/2010/3/14/crazy-heretical-and-awesome-the-way-i-write-rails-apps.html

• http://objectsonrails.com/

Questions?