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

# File activerecord/lib/active_record/inheritance.rb, line 124
def abstract_class?
  defined?(@abstract_class) && @abstract_class == true
end

Returns whether this class is an abstract class or not.

base_class() Show source

# File activerecord/lib/active_record/inheritance.rb, line 94
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

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

If A extends ActiveRecord::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.

descends_from_active_record?() Show source

# File activerecord/lib/active_record/inheritance.rb, line 71
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

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

new(*args, &block) Show source

# File activerecord/lib/active_record/inheritance.rb, line 48
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 has_attribute?(inheritance_column)
    subclass = subclass_from_attributes(attrs)

    if subclass.nil? && base_class == self
      subclass = subclass_from_attributes(column_defaults)
    end
  end

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

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

sti_name() Show source

# File activerecord/lib/active_record/inheritance.rb, line 128
def sti_name
  store_full_sti_class ? name : name.demodulize
end

Protected Instance Methods

compute_type(type_name) Show source

# File activerecord/lib/active_record/inheritance.rb, line 136
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|
      constant = ActiveSupport::Dependencies.safe_constantize(candidate)
      return constant if candidate == constant.to_s
    end

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

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.