How to get the my_var model variable:

puts self.var

or

puts var

How to set the my_var model variable:

self.var = "new value"

Note that when setting, you must prefix with self., unlike when getting. Also note that @var will not work for setting or getting model data, ever.

As part of my ongoing professional education, I’ve decided to read through several Ruby on Rails projects on Github. It has been a great experience, and I am learning a lot. It’s insightful to see where I’m better than other software architects, and where I have room to grow – there are some very nuanced lessons to learn, and some very simple ones. This is one of the very simple ones.

• If you use :dependent => :destroy in your Rails model, each model to be destroyed will be instantiated and the destroy() method will be called upon it. This will result in the normal object destruction lifecycle, include any callbacks. Destroying children and grandchildren can be handled gracefully. It is a safe, normal way to destroy objects. If you’re not sure whether to use :dependent => :destroy or :dependent => :delete_all, use :dependent => destroy.
• If you use :dependent => :delete_all in your Rails model, no objects will be loaded into memory and no destroy() methods will be called. Instead, a simple SQL query along the lines of DELETE * FROM dependent_model where depending_model_id = N will be run. There is no concern paid to destroying children and grandchildren; they will be orphaned in the database. If constructing a dependend model object and invoking destroy() is slow, or you simply wish to bypass the normal object destruction lifecycle, this is your best choice.

Instead, use:

create_table :address do |t|
  t.references :person
end

After 9 years of writing Ruby on Rails code, link_to() never ceases to trip me up. Does it trip you up, too? Here are some quick notes:

1. The first argument is what you want inside the <a> tag. For example link_to("today's news") produces <a>today's news</a>
2. The second argument is the href attribute value. For example, link_to("today's news", "www.news.com") produces <a href="www.news.com">today's news</a>
3. The third argument is a hash that contains everything else – most importantly, your <a> tag attributes. For example, link_to("today's news", "www.news.com", {id: "newsbox", class: "infos"}) produces <a id="newsbox" class="infos" href="www.news.com">today's news</a>. The third argument can contain many other options, of which I have never been able to find a definitive list.

Introduced in Rails 4, the ./bin directory contains your app’s “binstubs.” Binstubs are wrappers around gem executables, like rails or bundle, which ensures a gem executable is run inside the correct environment for your Rails app.

When a new Ruby on Rails project is created with rails new, many files and folders are created inside your project folder. Here’s a quick reference of what those are.

rake -T -A

This command will print out all available rake tasks. You can use it with Rails’ Rakefile, or with a custom Rakefile. N.B.: not all tasks have descriptions, and that is okay.

PostgreSQL.

(Updated for 2015.)

• Don’t confuse attr_accessor and attr_accessible – they have very similar names
• attr_accessor is a pure Ruby function to create reader and writer methods for an instance variable
• attr_accessible is a pre-Rails 4 function to list the model attributes (e.g., database fields) that can be set via mass assignment, providing access control

You can use attr_accessor on a Rails model to create non-persisted instance variables. For example:

class Stock
  attr_accessor :current_price
end

This allows you to get the @current_price of a stock – something that would make no sense to persist.

ActiveRecord::Base.transaction do
  savings.withdrawal(100)
  checking.deposit(100)
end

If any exceptions are raised, the entire operation is rolled back on the database layer and nothing will be committed to the database.

No.

(Don’t believe me? Google it.)