Class: Class

Inherits:
Object show all
Defined in:
lib/active_support/core_ext/duplicable.rb,
lib/active_support/core_ext/class/removal.rb,
lib/active_support/core_ext/class/attribute_accessors.rb,
lib/active_support/core_ext/class/delegating_attributes.rb,
lib/active_support/core_ext/class/inheritable_attributes.rb

Overview

Allows attributes to be shared within an inheritance hierarchy, but where each descendant gets a copy of their parents' attributes, instead of just a pointer to the same. This means that the child can add elements to, for example, an array without those additions being shared with either their parent, siblings, or children, which is unlike the regular class-level attributes that are shared across the entire hierarchy.

Constant Summary collapse

EMPTY_INHERITABLE_ATTRIBUTES =

Prevent this constant from being created multiple times

{}.freeze

Instance Method Summary collapse

Instance Method Details

#cattr_accessor(*syms) ⇒ Object


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# File 'lib/active_support/core_ext/class/attribute_accessors.rb', line 50

def cattr_accessor(*syms)
  cattr_reader(*syms)
  cattr_writer(*syms)
end

#cattr_reader(*syms) ⇒ Object


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# File 'lib/active_support/core_ext/class/attribute_accessors.rb', line 10

def cattr_reader(*syms)
  syms.flatten.each do |sym|
    next if sym.is_a?(Hash)
    class_eval(<<-EOS, __FILE__, __LINE__)
      unless defined? @@#{sym}
        @@#{sym} = nil
      end

      def self.#{sym}
        @@#{sym}
      end

      def #{sym}
        @@#{sym}
      end
    EOS
  end
end

#cattr_writer(*syms) ⇒ Object


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# File 'lib/active_support/core_ext/class/attribute_accessors.rb', line 29

def cattr_writer(*syms)
  options = syms.extract_options!
  syms.flatten.each do |sym|
    class_eval(<<-EOS, __FILE__, __LINE__)
      unless defined? @@#{sym}
        @@#{sym} = nil
      end

      def self.#{sym}=(obj)
        @@#{sym} = obj
      end

      #{"
      def #{sym}=(obj)
        @@#{sym} = obj
      end
      " unless options[:instance_writer] == false }
    EOS
  end
end

#class_inheritable_accessor(*syms) ⇒ Object


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# File 'lib/active_support/core_ext/class/inheritable_attributes.rb', line 76

def class_inheritable_accessor(*syms)
  class_inheritable_reader(*syms)
  class_inheritable_writer(*syms)
end

#class_inheritable_array(*syms) ⇒ Object


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# File 'lib/active_support/core_ext/class/inheritable_attributes.rb', line 81

def class_inheritable_array(*syms)
  class_inheritable_reader(*syms)
  class_inheritable_array_writer(*syms)
end

#class_inheritable_array_writer(*syms) ⇒ Object


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# File 'lib/active_support/core_ext/class/inheritable_attributes.rb', line 42

def class_inheritable_array_writer(*syms)
  options = syms.extract_options!
  syms.each do |sym|
    class_eval <<-EOS
      def self.#{sym}=(obj)
        write_inheritable_array(:#{sym}, obj)
      end

      #{"
      def #{sym}=(obj)
        self.class.#{sym} = obj
      end
      " unless options[:instance_writer] == false }
    EOS
  end
end

#class_inheritable_hash(*syms) ⇒ Object


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# File 'lib/active_support/core_ext/class/inheritable_attributes.rb', line 86

def class_inheritable_hash(*syms)
  class_inheritable_reader(*syms)
  class_inheritable_hash_writer(*syms)
end

#class_inheritable_hash_writer(*syms) ⇒ Object


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# File 'lib/active_support/core_ext/class/inheritable_attributes.rb', line 59

def class_inheritable_hash_writer(*syms)
  options = syms.extract_options!
  syms.each do |sym|
    class_eval <<-EOS
      def self.#{sym}=(obj)
        write_inheritable_hash(:#{sym}, obj)
      end

      #{"
      def #{sym}=(obj)
        self.class.#{sym} = obj
      end
      " unless options[:instance_writer] == false }
    EOS
  end
end

#class_inheritable_reader(*syms) ⇒ Object


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# File 'lib/active_support/core_ext/class/inheritable_attributes.rb', line 10

def class_inheritable_reader(*syms)
  syms.each do |sym|
    next if sym.is_a?(Hash)
    class_eval <<-EOS
      def self.#{sym}
        read_inheritable_attribute(:#{sym})
      end

      def #{sym}
        self.class.#{sym}
      end
    EOS
  end
end

#class_inheritable_writer(*syms) ⇒ Object


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# File 'lib/active_support/core_ext/class/inheritable_attributes.rb', line 25

def class_inheritable_writer(*syms)
  options = syms.extract_options!
  syms.each do |sym|
    class_eval <<-EOS
      def self.#{sym}=(obj)
        write_inheritable_attribute(:#{sym}, obj)
      end

      #{"
      def #{sym}=(obj)
        self.class.#{sym} = obj
      end
      " unless options[:instance_writer] == false }
    EOS
  end
end

#duplicable?Boolean

Returns:

  • (Boolean)

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# File 'lib/active_support/core_ext/duplicable.rb', line 40

def duplicable?
  false
end

#inheritable_attributesObject


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# File 'lib/active_support/core_ext/class/inheritable_attributes.rb', line 91

def inheritable_attributes
  @inheritable_attributes ||= EMPTY_INHERITABLE_ATTRIBUTES
end

#read_inheritable_attribute(key) ⇒ Object


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# File 'lib/active_support/core_ext/class/inheritable_attributes.rb', line 112

def read_inheritable_attribute(key)
  inheritable_attributes[key]
end

#remove_class(*klasses) ⇒ Object

Removes the classes in klasses from their parent module.

Ordinary classes belong to some module via a constant. This method computes that constant name from the class name and removes it from the module it belongs to.

Object.remove_class(Integer) # => [Integer]
Integer                      # => NameError: uninitialized constant Integer

Take into account that in general the class object could be still stored somewhere else.

i = Integer                  # => Integer
Object.remove_class(Integer) # => [Integer]
Integer                      # => NameError: uninitialized constant Integer
i.subclasses                 # => ["Bignum", "Fixnum"]
Fixnum.superclass            # => Integer

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# File 'lib/active_support/core_ext/class/removal.rb', line 36

def remove_class(*klasses)
  klasses.flatten.each do |klass|
    # Skip this class if there is nothing bound to this name
    next unless defined?(klass.name)
    
    basename = klass.to_s.split("::").last
    parent = klass.parent
    
    # Skip this class if it does not match the current one bound to this name
    next unless parent.const_defined?(basename) && klass = parent.const_get(basename)

    parent.instance_eval { remove_const basename } unless parent == klass
  end
end

#remove_subclassesObject

Unassociates the class with its subclasses and removes the subclasses themselves.

Integer.remove_subclasses # => [Bignum, Fixnum]
Fixnum                    # => NameError: uninitialized constant Fixnum

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# File 'lib/active_support/core_ext/class/removal.rb', line 8

def remove_subclasses
  Object.remove_subclasses_of(self)
end

#reset_inheritable_attributesObject


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# File 'lib/active_support/core_ext/class/inheritable_attributes.rb', line 116

def reset_inheritable_attributes
  @inheritable_attributes = EMPTY_INHERITABLE_ATTRIBUTES
end

#subclassesObject

Returns an array with the names of the subclasses of self as strings.

Integer.subclasses # => ["Bignum", "Fixnum"]

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# File 'lib/active_support/core_ext/class/removal.rb', line 15

def subclasses
  Object.subclasses_of(self).map { |o| o.to_s }
end

#superclass_delegating_accessor(*names) ⇒ Object


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# File 'lib/active_support/core_ext/class/delegating_attributes.rb', line 42

def superclass_delegating_accessor(*names)
  superclass_delegating_reader(*names)
  superclass_delegating_writer(*names)
end

#superclass_delegating_reader(*names) ⇒ Object


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# File 'lib/active_support/core_ext/class/delegating_attributes.rb', line 8

def superclass_delegating_reader(*names)
  class_name_to_stop_searching_on = self.superclass.name.blank? ? "Object" : self.superclass.name
  names.each do |name|
    class_eval <<-EOS
    def self.#{name}
      if defined?(@#{name})
        @#{name}
      elsif superclass < #{class_name_to_stop_searching_on} && superclass.respond_to?(:#{name})
        superclass.#{name}
      end
    end
    def #{name}
      self.class.#{name}
    end
    def self.#{name}?
      !!#{name}
    end
    def #{name}?
      !!#{name}
    end
    EOS
  end
end

#superclass_delegating_writer(*names) ⇒ Object


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# File 'lib/active_support/core_ext/class/delegating_attributes.rb', line 32

def superclass_delegating_writer(*names)
  names.each do |name|
    class_eval <<-EOS
      def self.#{name}=(value)
        @#{name} = value
      end
    EOS
  end
end

#write_inheritable_array(key, elements) ⇒ Object


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# File 'lib/active_support/core_ext/class/inheritable_attributes.rb', line 102

def write_inheritable_array(key, elements)
  write_inheritable_attribute(key, []) if read_inheritable_attribute(key).nil?
  write_inheritable_attribute(key, read_inheritable_attribute(key) + elements)
end

#write_inheritable_attribute(key, value) ⇒ Object


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# File 'lib/active_support/core_ext/class/inheritable_attributes.rb', line 95

def write_inheritable_attribute(key, value)
  if inheritable_attributes.equal?(EMPTY_INHERITABLE_ATTRIBUTES)
    @inheritable_attributes = {}
  end
  inheritable_attributes[key] = value
end

#write_inheritable_hash(key, hash) ⇒ Object


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# File 'lib/active_support/core_ext/class/inheritable_attributes.rb', line 107

def write_inheritable_hash(key, hash)
  write_inheritable_attribute(key, {}) if read_inheritable_attribute(key).nil?
  write_inheritable_attribute(key, read_inheritable_attribute(key).merge(hash))
end