module ActiveRecord::Inheritance::ClassMethods

Attributes

abstract_class[RW]

Set this to true if this is an abstract class (see abstract_class?). If you are using inheritance with ActiveRecord and don't want child classes to utilize the implied STI table name of the parent class, this will need to be true. For example, given the following:

class SuperClass < ActiveRecord::Base
  self.abstract_class = true
end
class Child < SuperClass
  self.table_name = 'the_table_i_really_want'
end

self.abstract_class = true is required to make Child<.find,.create, or any Arel method> use the_table_i_really_want instead of a table called super_classes

Public Instance Methods

abstract_class?() Show source

Returns whether this class is an abstract class or not.

# File activerecord/lib/active_record/inheritance.rb, line 99
def abstract_class?
  defined?(@abstract_class) && @abstract_class == true
end

base_class() Show source

Returns the class descending directly from ActiveRecord::Base, or an abstract class, if any, in the inheritance hierarchy.

If A extends AR::Base, A.base_class will return A. If B descends from A through some arbitrarily deep hierarchy, B.base_class will return A.

If B < A and C < B and if A is an #abstract_class then both B.base_class and C.base_class would return B as the answer since A is an abstract_class.

# File activerecord/lib/active_record/inheritance.rb, line 69
def base_class
  unless self < Base
    raise ActiveRecordError, "#{name} doesn't belong in a hierarchy descending from ActiveRecord"
  end

  if superclass == Base || superclass.abstract_class?
    self
  else
    superclass.base_class
  end
end

descends_from_active_record?() Show source

Returns true if this does not need STI type condition. Returns false if STI type condition needs to be applied.

# File activerecord/lib/active_record/inheritance.rb, line 36
def descends_from_active_record?
  if self == Base
    false
  elsif superclass.abstract_class?
    superclass.descends_from_active_record?
  else
    superclass == Base || !columns_hash.include?(inheritance_column)
  end
end

new(*args, &block) Show source

Determines if one of the attributes passed in is the inheritance column, and if the inheritance column is attr accessible, it initializes an instance of the given subclass instead of the base class.

Calls superclass method

# File activerecord/lib/active_record/inheritance.rb, line 17
def new(*args, &block)
  if abstract_class? || self == Base
    raise NotImplementedError, "#{self} is an abstract class and cannot be instantiated."
  end

  attrs = args.first
  if subclass_from_attributes?(attrs)
    subclass = subclass_from_attributes(attrs)
  end

  if subclass
    subclass.new(*args, &block)
  else
    super
  end
end

sti_name() Show source

# File activerecord/lib/active_record/inheritance.rb, line 103
def sti_name
  store_full_sti_class ? name : name.demodulize
end

symbolized_base_class() Show source

# File activerecord/lib/active_record/inheritance.rb, line 51
def symbolized_base_class
  ActiveSupport::Deprecation.warn("ActiveRecord::Base.symbolized_base_class is deprecated and will be removed without replacement.")
  @symbolized_base_class ||= base_class.to_s.to_sym
end

symbolized_sti_name() Show source

# File activerecord/lib/active_record/inheritance.rb, line 56
def symbolized_sti_name
  ActiveSupport::Deprecation.warn("ActiveRecord::Base.symbolized_sti_name is deprecated and will be removed without replacement.")
  @symbolized_sti_name ||= sti_name.present? ? sti_name.to_sym : symbolized_base_class
end

Protected Instance Methods

compute_type(type_name) Show source

Returns the class type of the record using the current module as a prefix. So descendants of MyApp::Business::Account would appear as MyApp::Business::AccountSubclass.

# File activerecord/lib/active_record/inheritance.rb, line 111
def compute_type(type_name)
  if type_name.match(/^::/)
    # If the type is prefixed with a scope operator then we assume that
    # the type_name is an absolute reference.
    ActiveSupport::Dependencies.constantize(type_name)
  else
    # Build a list of candidates to search for
    candidates = []
    name.scan(/::|$/) { candidates.unshift "#{$`}::#{type_name}" }
    candidates << type_name

    candidates.each do |candidate|
      begin
        constant = ActiveSupport::Dependencies.constantize(candidate)
        return constant if candidate == constant.to_s
      # We don't want to swallow NoMethodError < NameError errors
      rescue NoMethodError
        raise
      rescue NameError
      end
    end

    raise NameError.new("uninitialized constant #{candidates.first}", candidates.first)
  end
end