Guides.rubyonrails.org

$ bundle exec rake rdoc

# Declares an attribute reader backed by an internally-named
# instance variable.
def attr_internal_reader(*attrs)
  ...
end

If you need to use `return` statements in your callbacks, it is recommended that you explicitly define them as methods.

If `return` is needed it is recommended to explicitly define a method.

# Converts a collection of elements into a formatted string by
# calling +to_s+ on all elements and joining them.
#
#   Blog.all.to_formatted_s # => "First PostSecond PostThird Post"

# ==== Examples
#
#   Person.exists?(5)
#   Person.exists?('5')
#   Person.exists?(name: "David")
#   Person.exists?(['name LIKE ?', "%#{query}%"])

# For checking if an integer is even or odd.
#
#   1.even? # => false
#   1.odd?  # => true
#   2.even? # => true
#   2.odd?  # => false

#   label(:article, :title)
#   # => <label for="article_title">Title</label>
#
#   label(:article, :title, "A short title")
#   # => <label for="article_title">A short title</label>
#
#   label(:article, :title, "A short title", class: "title_label")
#   # => <label for="article_title" class="title_label">A short title</label>

#   polymorphic_url(record)  # same as comment_url(record)

`config.action_mailer.perform_deliveries` specifies whether mail will actually be delivered and is true by default

# Returns true if the collection is empty.
#
# If the collection has been loaded
# it is equivalent to <tt>collection.size.zero?</tt>. If the
# collection has not been loaded, it is equivalent to
# <tt>collection.exists?</tt>. If the collection has not already been
# loaded and you are going to fetch the records anyway it is better to
# check <tt>collection.length.zero?</tt>.
def empty?
  if loaded?
    size.zero?
  else
    @target.blank? && !scope.exists?
  end
end

config/routes.rb            # YES
routes.rb                   # NO
RAILS_ROOT/config/routes.rb # NO

class Array
  # Calls +to_param+ on all its elements and joins the result with
  # slashes. This is used by +url_for+ in Action Pack.
  def to_param
    collect { |e| e.to_param }.join '/'
  end
end

$ echo "+:to_param+" | rdoc --pipe
# => <p><code>:to_param</code></p>

# Runs all the validations within the specified context.
# Returns true if no errors are found, false otherwise.
#
# If the argument is false (default is +nil+), the context is
# set to <tt>:create</tt> if <tt>new_record?</tt> is true,
# and to <tt>:update</tt> if it is not.
#
# Validations with no <tt>:on</tt> option will run no
# matter the context. Validations with # some <tt>:on</tt>
# option will only run in the specified context.
def valid?(context = nil)
  ...
end

# * <tt>:allow_nil</tt> - Skip validation if attribute is +nil+.

for severity in Severity.constants
  class_eval <<-EOT, __FILE__, __LINE__
    def #{severity.downcase}(message = nil, progname = nil, &block)  # def debug(message = nil, progname = nil, &block)
      add(#{severity}, message, progname, &block)                    #   add(DEBUG, message, progname, &block)
    end                                                              # end
                                                                     #
    def #{severity.downcase}?                                        # def debug?
      #{severity} >= @level                                          #   DEBUG >= @level
    end                                                              # end
  EOT
end

# def self.find_by_login_and_activated(*args)
#   options = args.extract_options!
#   ...
# end
self.class_eval %{
  def self.#{method_id}(*args)
    options = args.extract_options!
    ...
  end
}

module ActiveRecord::Core::ClassMethods
  def arel_table #:nodoc:
    # do some magic..
  end
end

# image_tag("icon.png")
#   # => <img alt="Icon" src="/assets/icon.png" />