Module: ActiveRecord::Inheritance::ClassMethods

Defined in:
activerecord/lib/active_record/inheritance.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Instance Attribute Details

#abstract_classObject

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


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# File 'activerecord/lib/active_record/inheritance.rb', line 121

def abstract_class
  @abstract_class
end

Instance Method Details

#abstract_class?Boolean

Returns whether this class is an abstract class or not.

Returns:

  • (Boolean)

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# File 'activerecord/lib/active_record/inheritance.rb', line 124

def abstract_class?
  defined?(@abstract_class) && @abstract_class == true
end

#base_classObject

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.


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# 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

#descends_from_active_record?Boolean

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

Returns:

  • (Boolean)

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# 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

#finder_needs_type_condition?Boolean

:nodoc:

Returns:

  • (Boolean)

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# File 'activerecord/lib/active_record/inheritance.rb', line 81

def finder_needs_type_condition? #:nodoc:
  # This is like this because benchmarking justifies the strange :false stuff
  :true == (@finder_needs_type_condition ||= descends_from_active_record? ? :false : :true)
end

#new(*args, &block) ⇒ Object

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.


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# 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

#sti_nameObject


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# File 'activerecord/lib/active_record/inheritance.rb', line 128

def sti_name
  store_full_sti_class ? name : name.demodulize
end