Upgrading to Rails 5

There are lots of changes, so I just picked up some here.


belongs_to required by default.

# config/initializers/new_framework_defaults.rb
Rails.application.config.active_record.belongs_to_required_by_default = true

# app/models/post.rb
- belongs_to :user, required: true
+ belongs_to :user

But you need to care about it because of other gems. It sometimes doesn't work if one of gems is using a hook like ActiveRecord::Base.extend, ActiveRecord::Base.send :include etc intead of ActiveSupport.on_load(:active_record).


Change your mailers to inherit from your new ApplicationMailer.

# app/mailers/application_mailer.rb
class ApplicationMailer < ActionMailer::Base
  default from: ''
  layout 'mailer' #=> app/views/layouts/mailer.html.erb or mailer.txt.erb

Default values in initializers

Setup the default locale, generators etc from an initializer instead of config/application.rb

# config/initializers/locale.rb
Rails.application.config.i18n.available_locales = [:en, :ja]
Rails.application.config.i18n.default_locale = :en

# config/initializers/generators.rb
Rails.application.config.generators do |g|
  g.stylesheet_engine :sass
  g.template_engine :slim

But you shouldn't assign some values such as time_zone in an initializer. Because Rails.application.config.time_zone will work, but won't. Time.zone_default is assgined before the initializer.

In general, configuration specific to the application object needs to go either in config/application.rb or in config/environments/#{Rails.env}.rb, you can't just assign to an arbitrary config point in config/initializers and expect it to work.

# config/application.rb
module Foo
  class Application < Rails::Application
    config.time_zone = 'UTC'
    config.paths.add 'lib', eager_load: true

Quiet assets

You don't need quiet_assets gem finally! Logger output is suppressed using Rails.application.config.assets.prefix path to match.
rails/rails#25351, rails/sprockets-rails#355

# config/environments/development.rb
# Suppress logger output for asset requests.
config.assets.quiet = true

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