Module: ActiveRecord::Inheritance::ClassMethods

Defined in:
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


93
94
95
# File 'lib/active_record/inheritance.rb', line 93

def abstract_class
  @abstract_class
end

Instance Method Details

#abstract_class?Boolean

Returns whether this class is an abstract class or not.

Returns:

  • (Boolean)

96
97
98
# File 'lib/active_record/inheritance.rb', line 96

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 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.


66
67
68
69
70
71
72
73
74
75
76
# File 'lib/active_record/inheritance.rb', line 66

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

True if this isn't a concrete subclass needing a STI type condition.

Returns:

  • (Boolean)

35
36
37
38
39
40
41
42
43
# File 'lib/active_record/inheritance.rb', line 35

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)

45
46
47
48
# File 'lib/active_record/inheritance.rb', line 45

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


17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
# File 'lib/active_record/inheritance.rb', line 17

def new(*args, &block)
  if abstract_class? || self == Base
    raise NotImplementedError, "#{self} is an abstract class and can not 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_nameObject


100
101
102
# File 'lib/active_record/inheritance.rb', line 100

def sti_name
  store_full_sti_class ? name : name.demodulize
end

#symbolized_base_classObject


50
51
52
# File 'lib/active_record/inheritance.rb', line 50

def symbolized_base_class
  @symbolized_base_class ||= base_class.to_s.to_sym
end

#symbolized_sti_nameObject


54
55
56
# File 'lib/active_record/inheritance.rb', line 54

def symbolized_sti_name
  @symbolized_sti_name ||= sti_name.present? ? sti_name.to_sym : symbolized_base_class
end