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A Few Tips For Getting Started With Rails

Ruby on Rails
by: Tyler Hoffman

Article summary

Rails does a lot of work for you. This is often beneficial, but when it makes assumptions that aren’t right for your app, it can be frustrating. In this post, I’ll discuss a few issues that can arise when you get started creating models, along with some easy solutions to them. Oh, and before I get too far, I should note that the code here assumes you are using Rails 5.

Custom Pluralization

Rails handles pluralization for you in a lot of cases. For example, when you generate a model, it creates a number of additional files, some of which have the plural version of the model’s name. For example, if you generate a Computer model it will create a few files, some of which have the word “computers” in the name. 

$ rails g model Computer
Running via Spring preloader in process 71634
      invoke  active_record
      create    db/migrate/20161005132000_create_computers.rb
      create    app/models/computer.rb
      invoke    test_unit
      create      test/models/computer_test.rb
      create      test/fixtures/computers.yml

Additionally, if you were to create another model that had a has_many relationship with Computer, you would reference the Computer model by its plural version.

has_many :computers

This usually goes smoothly, but there are times when things just don’t work right. For example, let’s create a Superhero class:

rails g model Superhero

This produces the following output:

$ rails g model Superhero
Running via Spring preloader in process 6027
      invoke  active_record
      create    db/migrate/20160929235358_create_superheros.rb
      create    app/models/superhero.rb
      invoke    test_unit
      create      test/models/superhero_test.rb
      create      test/fixtures/superheros.yml

We run into a surprising problem: the pluralization is incorrect. Rails provides an easy way to fix this issue, though: inflections. Among other things, inflections allow us to transform strings between their plural and singular forms. We can define the correct pluralization of superhero in config/initializers/inflections.rb by adding the following code:

ActiveSupport::Inflector.inflections() do |inflect|
  inflect.irregular 'hero', 'heroes'
end

Once this is in place, pluralization works correctly throughout your app.

Associations and Foreign Keys

You often want relationships between your models. For instance, if a superhero you belongs to a team, you could build the migration for your model as follows.

class CreateSuperheroes < ActiveRecord::Migration[5.0]
  def change
    create_table :superhero do |t|
      t.belongs_to :super_team
      t.timestamps
    end
  end
end

This is pretty similar to what you will see in just about any intro tutorial on rails. It creates an association between SuperTeams and Superheroes. When I first saw this, I assumed it was creating a foreign key constraints in the database. However, this is not the case. If you want foreign key constraints, you'll have to explicitly tell rails. To do so, the following line of code can be added after create_table is called:

add_foreign_key :teams_memberships, :superheroes

Now the migration actually adds foreign key constraints, so the relationship is preserved, even when accessing the database outside of rails.

Associations With Custom Names

When you get started with associations in rails, a lot of the documentation you see will assume that associations have the same name as the class they link to. For instance, let's say we're creating an app to represent businesses, and that we've already created an Employee model. When we create our Business model, we'll likely want each business to have a manager.

We will want a belongs_to association to represent this relationship. In the Business model, we could might start off with the following:

belongs_to, :employee

This does create the association, but it will name it "employee," which is not desirable. If we want to name the association "manager," we could change the association to look like this:

belongs_to, :manager, class_name: 'Employee'

Now we have an association to the correct model with the desired name.

Hopefully this has been helpful and will save you a bit of time when developing on Rails in the future.

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