serodriguez68

Practical Object-Oriented Design in Ruby - Notes

Notes by: Sergio Rodriguez Book by: Sandi Metz

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Chapter 1 - Object Oriented Design

Why Design?

• Changes in applications are unavoidable.
• Change is hard because of the dependencies between objects
• The sender of the message knows things about the receiver

serodriguez68

How to make a Rails application rails db:reset itself on Heroku

Imagine you have some type of demo that needs to reset itself once a day.

1. Install the Database Cleaner Gem and make sure you make it available for the production environment.

2. Create a lib/tasks/scheduler.rake file that looks similar to this

desc "This task is called by the Heroku scheduler add-on to reset the demo"
task :reset_demo => :environment do
  puts "Cleaning Up The DB..."

serodriguez68

Dependency Injection with defaults in Ruby by overriding the new method

This technique his heavilly inspired by Tom Dalling's Dependency Injection Containers vs Hard-coded Constants article. In particular, it proposes an alternative implementation of his "Hybrid Approach" using a build class method.

The main problems with Tom's implementation using build

• It introduces a new way of instantiating objects via the .build method. This new API requires other developers to be aware that they must use .build if they want an instance of the object with default dependencies.
• Following from the point above, in cases where we want to use cascading default dependencies, we must remember to use the dependencies .build method to benefit from their default behaviour.

Our approach: overriding .new

serodriguez68

What parameters should go in the initialisation method? Objects that "be" VS Objects that "do"

Tim Riley has a great rule of thumb for classifying objects and deciding what parameters should be part of the class' attributes (state) VS which should be provided as arguments to the methods of that class.

There are 2 types of Objects: Objects that "be" and Objects that "do".

Objects that "be"

If you say "this object IS a dog", then you are dealing with an object that "be".

The job of these objects are to represent data in our application. They hold data in their state and therefore we must

serodriguez68

1. About

This work is related to my post about the status of encrypted credentials support in Rails 6 that is part of the "A May of WTFs" initiative.

In particular, it identifies the documentation gaps that exist in Rails' 6.0.3.1 guides related to encrypted credentials.

2. Documentation Gaps and Suggestions

Guide: Configuring Rails Applications > Section: 3.1 Rails General Configuration