R A I L S O N M A U I

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Concerns, Decorators, Presenters, Service Objects, Helpers, Help me Decide!

RailsConf 2014 Chicago

April 22, 2014 !

Justin Gordon @railsonmaui

Rails Consultant www.railsonmaui.com

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ControllerModel &

Avoid the Ball of Mud

May seem fun… !

Guaranteed: the perpetrator is

not doing the cleanup!

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• Show Redmine, • AccountsController, lost_password action • UserModel, big class, 762 Lines

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Sandi Rules method > 5 lines class > 100 lines 😱

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How do we organize the mess?

Organizational Conventions Matter

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Department Store

What if the clothing store was organized by color? What if a clothing store was organized by size?

Organizational Conventions Matter

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Thrift Store

What if no organization?

Like Fashion… Coding Style ➜ Personal Preference

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• Coding is like writing! • Tons of disagreement in the Rails community over names, patterns, etc. • But let’s agree on a few things..

And Our Style is…

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Prefer the Rails default framework (Models, Model Concerns, Controllers, Controller Concerns) Know Rails really well! Assume team members also know rails!

DHH QuoteJG: "This is starting to boil down to utilize the framework capabilities and move beyond only when necessary.”

DHH: "Which is really just an extension of KISS (Keep It Simple, Stupid). When you use the framework code for what it’s intended, you’re not cutting against the grain. You don’t need to write as much code. It’s clearer to everyone because it’s the same approach everyone else is taking."

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Microposts Example

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Micropost Model

User Model

Micropost Controller

User Controller

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Refactoring Examples in Pull Requests

• https://github.com/justin808/fat-code-refactoring-techniques/pulls

• Based on Michael Hartl’s “Rails Tutorial” MicroBlog example application

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• Github PRs are the most AMAZING place to discuss code! • Clean up the Microblog code a little, demonstrating: Concerns, Decorators, and Presenters. • Refactor Micropost Create Action (fat controller method)

Objectives

Patterns & Techniques

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DRY

Methods < 5 Lines

Classes < 100 lines

One Instance Variable in View

Easy to Test

ConcernsDraper

Decorators

Validation Classes

Presenters

Split-up Controllers

ClarityEasy to Change

Guidelines

Move Logic to Models

Easy to Find

Where we’re going with this talk…The first technique is Concerns.

• Huge model file with even larger spec file.

• Break up the model/spec using Rails concerns. Try to break it up by domain, but any logical split will help.

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Scenario

If you will have multiple concerns for only one model, group the concerns inside of a module.

Scenario

• You’ve got duplicated code in two models, different database tables.

• Tease out a concern that applies to both models. Since your

models extend ActiveRecord::Base, using regular

inheritance is problematic. Instead, use a concern.

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Rails Concerns

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Big Model

class macros (has_many, validates, etc.)

instance methods

class methods

Rails Concerns

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Big Model

some-domain class macros

some-domain instance methods

some-domain class methods

other class macros

other instance methods

other class methods

Domain Concern

some-domain class macrossome-domain instance methodssome-domain class methods

Mix-ins on models and controllers. Mention controllers as well as models.

Concerns: How

• Discover set of related code for a problem domain

• Create a module with extends ActiveSupport::Concern

• Move code into the Concern

• Break out tests into corresponding test file for the Concern

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Simple, safe, easy “refactoring” You could use Ruby’s “include”, “included”, and “extend”… But, not as simple

DHH on Domain vs. Technical Refactoring

"I’ve not yet found a case where the scope of the current file/class couldn’t be brought under control by using a domain-driven extraction approach."

"In a sea of 60 methods, there will always be domain-based groupings, rather than technical groupings. Never seen that not be the case."

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"There’s not going to be one solution to all big files. My preferred default is “break up using DOMAIN concerns (not technical ones)”, unless there’s a “missing object” screaming to be liberated."

Concerns: Example

• Break out Emailable Concern out of User model

• Captures domain logic of lower case emails on user model

• Benefits: Smaller model, smaller spec

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Objectives

Patterns & Techniques

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DRY

Methods < 5 Lines

Classes < 100 lines

One Instance Variable in View

Easy to Test

ConcernsDraper

Decorators

Validation Classes

Presenters

Split-up Controllers

ClarityEasy to Change

Guidelines

Move Logic to Models

Easy to Find

Where we’re going with this talk…

Scenario

• Model file creating detailed validation messages with HTML tags and URL links.

• Move the message creation code into a Draper Decorator for the model. These decorators work great for model based presentation code.

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Draper Decorators

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Mode and Model-

Concerns

Presentation Code (views,

helpers)

Draper Decorators

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Mode and Model-

Concerns

Presentation Code (views,

helpers)

Draper Decorators

Draper Decorators: What?

• Popular gem that facilitates model decorators

• Very simple, easy to use

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Draper Decorators: Why?• Removing presentation code from your model or model-

concerns

• Consolidating some helper, view, controller methods by models

• Presentation code relating to one model, but multiple controllers/views

• Consolidation of flash messages related to a given model

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Draper Decorators: Why• Decorators are the ideal place to:

• format complex data for user display

• define commonly-used representations of an object, like a name method that combines first_name and last_name attributes

• mark up attributes with a little semantic HTML, like turning a url field into a hyperlink

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Draper Decorators: Alternatives

• View Helpers

• PORO, getting a handle to the controller or view

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Example

Several views have code that format the micropost.created_at: !

Posted <%= time_ago_in_words(micropost.created_at) %> ago.

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Scenario• You have duplicated rendering code in several files.

• Remedy:

1. If rendering code, use a partial.

2. If ruby code, use either a view helper or create a static method on a utility class. View helpers have access other helpers. Utility classes require extra work to call view context methods.

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Objectives

Patterns & Techniques

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DRY

Methods < 5 Lines

Classes < 100 lines

One Instance Variable in View

Easy to Test

ConcernsDraper

Decorators

Validation Classes

Presenters

Split-up Controllers

ClarityEasy to Change

Guidelines

Move Logic to Models

Easy to Find

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Scenario

• You are setting too many instance variables in the controller action. You also have local variables being assigned in the view.

• Presenter pattern: Create a PORO that wraps up the values and logic going from the controller to the view.

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Scenario

• Fragment caching in your view, but some extra queries still run

• Use the Presenter pattern, with memoization in the instance methods.

• @foobar ||= calculate_foobar

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Problem is the queries are invoked before the cache block.

Presenters

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Presenter Object Wrapping Data Needed by View

Smaller Controller Action Creating Only the Presenter Instance

Big Controller Action Setting Many Instance

Variables

View with ONE Instance Variable

View with MANY Instance Variables

beforeafter

Scenario• Problem: A controller file is huge with many actions and many more

private methods.

• Solution:

1. Split up the controller into multiple files by having your routing file map to different controllers.

2. Put any common functionality in a controller concern, similar to how you would do it for a model. An alternative is having an inheritance hierarchy of controllers. Mix-ins are more flexible.

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Scenario• Problem:

• Your Presenter class needs to access the view context, but it’s PORO.

• Solution:

1. Use this include in your PORO: “include Draper::ViewHelpers”.

2. Pass the controller instance into the constructor of the Presenter (include required helpers in controller), or set the view context in the view file.

3. Pass the view context into the methods that need it on the Presenter.

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Objectives

Patterns & Techniques

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DRY

Methods < 5 Lines

Classes < 100 lines

One Instance Variable in View

Easy to Test

ConcernsDraper

Decorators

Validation Classes

Presenters

Split-up Controllers

ClarityEasy to Change

Guidelines

Move Logic to Models

Easy to Find

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If a minor posts profane words: !

1. The post shall not be valid. 2. A counter will track how many times the

minor tried to use profanity. 3. The minor's parents shall be notified. 4. A special flash alert will alert the minor to

profanity usage.

Business Case

Original Idea is to show refactoring to Service Objects!

–David Heinemeier Hansson

“I've yet to see a compelling "make action a service object" example in the wild. Maybe they exist somewhere, though. Then again,

maybe unicorns are real too.”

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https://gist.github.com/dhh/10022098

Service Objects?

Service Objects Example

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Big Micropost Create Action on Controller

MicropostCreationService

ControllerResponse Flash, Flash-now, status code

Tiny Micropost Create Action on

Controller

https://github.com/justin808/fat-code-refactoring-techniques/pull/6

beforeafter

Created class ControllerResponse to package up the return message from the “ServiceObject” to the controller. Too much overlap with Controller!

A Bit Humbling…DHH: "Sorry to keep shooting the patterns down, but this is exactly what I mean when I say that most code does not need patterns, it just needs to be rewritten better."

JG: "I think it's a pattern either way. The pattern you presented is to use validators rather than a separate object."

DHH: Right, which Rails already has built in, and the code is easier to follow with less work.

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Single Purpose Controller• Controller with only one action

• https://github.com/justin808/fat-code-refactoring-techniques/pull/7

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Big Micropost Create Action on

Controller

Micropost Controller Just for Create

Rest of the Micropost Controller

Left too much biz logic in controller

DHH on Controllers“It’s [controller] intended to process the incoming request, fetch the model, and direct the user to a view or another action. If you’re yanking logic of that nature out of the controller, you’re

making an anemic controller. Shoving this into a service object is imo the lazy approach that doesn’t deliver any benefits in terms of simpler code. It imo is the sweep-it-under-the-rug approach.

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DHH on the work of a Controller

"I’ve yet to see compelling controller code that couldn’t be slimmed down by simply writing it better, spinning off another controller, or moving domain logic to the model. Here’s another example of a code ping pong I did off a convoluted action in RedMine: https://gist.github.com/dhh/10023987”

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Plain Rails

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Big Micropost Create Action on Controller

Micropost Model

User ModelSmall Micropost Create Action on

Controllerbefore

after

MicropostController interacts with both models. No extra classes. Move validation code and checks out of controller to model Move creation of flash message to decorator Move validation code to validation class

Scenario• Excessive model logic in complicated controller method.

• Either:

• Move model logic out of controller and into the models, utilizing Rails features such as validation.

• Create a non-AR based model to handle an interaction between two models (aka “Service Object”)

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POR (Plain Old Rails)• Use Rails Models, Validation, and Controller for their proper

jobs

• KISS (Keep It Simple Stupid)

• Don’t Invent Patterns That Don’t Need to be Invented

• Know the why of the Rails way

• Know the Rails way before deviating

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Refactoring Steps

• Move validation code and checks out of controller to model

• Move creation of flash message to decorator

• Move validation code to validation class

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References

• Rails Guides: http://guides.rubyonrails.org/

• Patterns to Refactor Fat ActiveRecord Models: http://blog.codeclimate.com/blog/2012/10/17/7-ways-to-decompose-fat-activerecord-models/

• DHH’s Example of 2 Controllers with Concerns: https://gist.github.com/dhh/10022098

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Thanks!Special thanks to those that helped review my code samples to this talk: @dhh, @jeg2, @gylaz, @jodosha, @dreamr, @thatrubylove, @therealadam, @robzolkos, Thoughtbot’s Learn program forum and Ruby Rogues Parley Forum

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Rails on Maui HQ, aka Sugar Ranch Maui

Thanks!• More details at my blog:

http://www.railsonmaui.com

• Feel free to contact me regarding your projects

• justin@railsonmaui.com

• http://airpair.me/railsonmaui

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