Class: Class

Inherits:
Object show all
Defined in:
lib/cassandra_mapper/core_ext/object/duplicable.rb,
lib/cassandra_mapper/core_ext/class/inheritable_attributes.rb,
lib/cassandra_mapper/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.

The copies of inheritable parent attributes are added to subclasses when they are created, via the inherited hook.

Constant Summary collapse

EMPTY_INHERITABLE_ATTRIBUTES =

Prevent this constant from being created multiple times

{}.freeze

Instance Method Summary collapse

Instance Method Details

#class_inheritable_accessor(*syms) ⇒ Object 



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# File 'lib/cassandra_mapper/core_ext/class/inheritable_attributes.rb', line 85

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/cassandra_mapper/core_ext/class/inheritable_attributes.rb', line 90

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/cassandra_mapper/core_ext/class/inheritable_attributes.rb', line 51

def class_inheritable_array_writer(*syms)
  options = syms.extract_options!
  syms.each do |sym|
    class_eval(<<-EOS, __FILE__, __LINE__ + 1)
      def self.#{sym}=(obj)                          # def self.levels=(obj)
        write_inheritable_array(:#{sym}, obj)        #   write_inheritable_array(:levels, obj)
      end                                            # end
                                                     #
      #{"                                            #
      def #{sym}=(obj)                               # def levels=(obj)
        self.class.#{sym} = obj                      #   self.class.levels = obj
      end                                            # end
      " unless options[:instance_writer] == false }  # # the writer above is generated unless options[:instance_writer] == false
    EOS
  end
end

#class_inheritable_hash(*syms) ⇒ Object 



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

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/cassandra_mapper/core_ext/class/inheritable_attributes.rb', line 68

def class_inheritable_hash_writer(*syms)
  options = syms.extract_options!
  syms.each do |sym|
    class_eval(<<-EOS, __FILE__, __LINE__ + 1)
      def self.#{sym}=(obj)                          # def self.nicknames=(obj)
        write_inheritable_hash(:#{sym}, obj)         #   write_inheritable_hash(:nicknames, obj)
      end                                            # end
                                                     #
      #{"                                            #
      def #{sym}=(obj)                               # def nicknames=(obj)
        self.class.#{sym} = obj                      #   self.class.nicknames = obj
      end                                            # end
      " unless options[:instance_writer] == false }  # # the writer above is generated unless options[:instance_writer] == false
    EOS
  end
end

#class_inheritable_reader(*syms) ⇒ Object

:nodoc:



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# File 'lib/cassandra_mapper/core_ext/class/inheritable_attributes.rb', line 16

def class_inheritable_reader(*syms)
  options = syms.extract_options!
  syms.each do |sym|
    next if sym.is_a?(Hash)
    class_eval(<<-EOS, __FILE__, __LINE__ + 1)
      def self.#{sym}                                # def self.after_add
        read_inheritable_attribute(:#{sym})          #   read_inheritable_attribute(:after_add)
      end                                            # end
                                                     #
      #{"                                            #
      def #{sym}                                     # def after_add
        self.class.#{sym}                            #   self.class.after_add
      end                                            # end
      " unless options[:instance_reader] == false }  # # the reader above is generated unless options[:instance_reader] == false
    EOS
  end
end

#class_inheritable_writer(*syms) ⇒ Object 



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# File 'lib/cassandra_mapper/core_ext/class/inheritable_attributes.rb', line 34

def class_inheritable_writer(*syms)
  options = syms.extract_options!
  syms.each do |sym|
    class_eval(<<-EOS, __FILE__, __LINE__ + 1)
      def self.#{sym}=(obj)                          # def self.color=(obj)
        write_inheritable_attribute(:#{sym}, obj)    #   write_inheritable_attribute(:color, obj)
      end                                            # end
                                                     #
      #{"                                            #
      def #{sym}=(obj)                               # def color=(obj)
        self.class.#{sym} = obj                      #   self.class.color = obj
      end                                            # end
      " unless options[:instance_writer] == false }  # # the writer above is generated unless options[:instance_writer] == false
    EOS
  end
end

#duplicable? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/cassandra_mapper/core_ext/object/duplicable.rb', line 56

def duplicable?
  false
end

#extlib_inheritable_accessor(*syms, &block) ⇒ Array[#to_s]

Defines class-level inheritable attribute accessor. Attributes are available to subclasses, each subclass has a copy of parent’s attribute.

Parameters:

  • *syms (Array[*#to_s, Hash{:instance_writer => Boolean}]) —

    Array of attributes to define inheritable accessor for.

  • syms (Hash) —

    a customizable set of options

Options Hash (*syms):

  • :instance_writer (Boolean) —

    if true, instance-level inheritable attribute writer is defined.

Returns:

  • (Array[#to_s]) —

    An Array of attributes turned into inheritable accessors.



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# File 'lib/cassandra_mapper/core_ext/class/inheritable_attributes.rb', line 228

def extlib_inheritable_accessor(*syms, &block)
  extlib_inheritable_reader(*syms)
  extlib_inheritable_writer(*syms, &block)
end

#extlib_inheritable_reader(*ivars, &block) ⇒ Array[#to_s]

TODO:

Do we want to block instance_reader via :instance_reader => false

TODO:

It would be preferable that we do something with a Hash passed in (error out or do the same as other methods above) instead of silently moving on). In particular, this makes the return value of this function less useful.

Defines class-level inheritable attribute reader. Attributes are available to subclasses, each subclass has a copy of parent’s attribute.

Parameters:

  • *syms (Array[#to_s]) —

    Array of attributes to define inheritable reader for.

Returns:

  • (Array[#to_s]) —

    Array of attributes converted into inheritable_readers.



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# File 'lib/cassandra_mapper/core_ext/class/inheritable_attributes.rb', line 165

def extlib_inheritable_reader(*ivars, &block)
  options = ivars.extract_options!

  ivars.each do |ivar|
    self.class_eval <<-RUBY, __FILE__, __LINE__ + 1
      def self.#{ivar}
        return @#{ivar} if self.object_id == #{self.object_id} || defined?(@#{ivar})
        ivar = superclass.#{ivar}
        return nil if ivar.nil? && !#{self}.instance_variable_defined?("@#{ivar}")
        @#{ivar} = ivar.duplicable? ? ivar.dup : ivar
      end
    RUBY
    unless options[:instance_reader] == false
      self.class_eval <<-RUBY, __FILE__, __LINE__ + 1
        def #{ivar}
          self.class.#{ivar}
        end
      RUBY
    end
    instance_variable_set(:"@#{ivar}", yield) if block_given?
  end
end

#extlib_inheritable_writer(*ivars) ⇒ Array[#to_s]

TODO:

We need a style for class_eval <<-HEREDOC. I’d like to make it class_eval(<<-RUBY, __FILE__, __LINE__), but we should codify it somewhere.

Defines class-level inheritable attribute writer. Attributes are available to subclasses, each subclass has a copy of parent’s attribute.

Parameters:

  • *syms (Array[*#to_s, Hash{:instance_writer => Boolean}]) —

    Array of attributes to define inheritable writer for.

  • syms (Hash) —

    a customizable set of options

Returns:

  • (Array[#to_s]) —

    An Array of the attributes that were made into inheritable writers.



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# File 'lib/cassandra_mapper/core_ext/class/inheritable_attributes.rb', line 200

def extlib_inheritable_writer(*ivars)
  options = ivars.extract_options!

  ivars.each do |ivar|
    self.class_eval <<-RUBY, __FILE__, __LINE__ + 1
      def self.#{ivar}=(obj)
        @#{ivar} = obj
      end
    RUBY
    unless options[:instance_writer] == false
      self.class_eval <<-RUBY, __FILE__, __LINE__ + 1
        def #{ivar}=(obj) self.class.#{ivar} = obj end
      RUBY
    end

    self.send("#{ivar}=", yield) if block_given?
  end
end

#inheritable_attributes ⇒ Object 



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# File 'lib/cassandra_mapper/core_ext/class/inheritable_attributes.rb', line 100

def inheritable_attributes
  @inheritable_attributes ||= EMPTY_INHERITABLE_ATTRIBUTES
end

#read_inheritable_attribute(key) ⇒ Object 



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# File 'lib/cassandra_mapper/core_ext/class/inheritable_attributes.rb', line 121

def read_inheritable_attribute(key)
  inheritable_attributes[key]
end

#reset_inheritable_attributes ⇒ Object 



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# File 'lib/cassandra_mapper/core_ext/class/inheritable_attributes.rb', line 125

def reset_inheritable_attributes
  @inheritable_attributes = EMPTY_INHERITABLE_ATTRIBUTES
end

#write_inheritable_array(key, elements) ⇒ Object 



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# File 'lib/cassandra_mapper/core_ext/class/inheritable_attributes.rb', line 111

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/cassandra_mapper/core_ext/class/inheritable_attributes.rb', line 104

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/cassandra_mapper/core_ext/class/inheritable_attributes.rb', line 116

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