module DuckRecord::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 DuckRecord 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 < DuckRecord::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?() click to toggle source

Returns whether this class is an abstract class or not.

# File lib/duck_record/inheritance.rb, line 88
def abstract_class?
  defined?(@abstract_class) && @abstract_class == true
end
base_class() click to toggle source

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

If A extends DuckRecord::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 lib/duck_record/inheritance.rb, line 58
def base_class
  unless self < Base
    raise DuckRecordError, "#{name} doesn't belong in a hierarchy descending from DuckRecord"
  end

  if superclass == Base || superclass.abstract_class?
    self
  else
    superclass.base_class
  end
end
inherited(subclass) click to toggle source
Calls superclass method
# File lib/duck_record/inheritance.rb, line 92
def inherited(subclass)
  subclass.instance_variable_set(:@_type_candidates_cache, Concurrent::Map.new)
  super
end
new(*args, &block) click to toggle 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 lib/duck_record/inheritance.rb, line 42
def new(*args, &block)
  if abstract_class? || self == Base
    raise NotImplementedError, "#{self} is an abstract class and cannot be instantiated."
  end

  super
end

Protected Instance Methods

compute_type(type_name) click to toggle 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 lib/duck_record/inheritance.rb, line 101
def compute_type(type_name)
  if type_name.start_with?("::".freeze)
    # 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
    type_candidate = @_type_candidates_cache[type_name]
    if type_candidate && type_constant = ActiveSupport::Dependencies.safe_constantize(type_candidate)
      return type_constant
    end

    # Build a list of candidates to search for
    candidates = []
    type_name.scan(/::|$/) { candidates.unshift "#{$`}::#{type_name}" }
    candidates << type_name

    candidates.each do |candidate|
      constant = ActiveSupport::Dependencies.safe_constantize(candidate)
      if candidate == constant.to_s
        @_type_candidates_cache[type_name] = candidate
        return constant
      end
    end

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